Estimated Influenza Illnesses, Medical Visits, Hospitalizations, and Deaths Averted by Vaccination in the United States

Introduction:

This web page provides estimates on the impact of annual influenza vaccination and the burden of influenza in the United States for the 2015-2016 influenza season, and will be updated annually.

For the past several years, CDC has used a model to estimate the numbers of influenza illnesses, medical visits, and hospitalizations, and the impact of influenza vaccination on these numbers in the United States (1-5). The methods used to calculate the estimates have been described previously (1,2) and are outlined briefly below. CDC uses the estimates of the burden of influenza in the population and the impact of influenza vaccination in influenza-related communications. Annual estimates on the number of influenza-related illnesses, medical visits, and hospitalizations, will be used to derive a five-year range to characterize the influenza burden in the United States. This range will be updated every five years.

Additionally, this web page provides estimates of influenza deaths and deaths averted by influenza vaccination. CDC calculates estimated influenza deaths in two ways: 1) using reports of pneumonia & influenza (P&I) deaths and 2) using reports of respiratory & circulatory (R&C) deaths attributable to influenza. P&I deaths are now available in real-time, while data on R&C deaths are available after a three-year delay. While both estimates are useful, P&I deaths represent only a fraction of the total number of deaths from influenza because they do not capture the deaths that occurred among people not tested for influenza or deaths that result from respiratory and cardiovascular complications. Calculations based on R&C deaths are used in CDC influenza-related communications materials because these calculations provide a more complete estimate of the actual burden of influenza. CDC will continue to present the mortality burden of influenza as a range, rather than a median or average, to better reflect the variability of influenza and will update estimates of R&C deaths as the data become available.

2015-2016 Estimates:

For the 2015-2016 influenza season, CDC estimates that influenza vaccination prevented approximately 5.1 million influenza illnesses, 2.5 million influenza-associated medical visits, and 71,000 influenza-associated hospitalizations (see Table 1). These estimates of averted disease burden are comparable to some previous seasons (see Table 2). During the 2015-2016 influenza season, CDC estimates that influenza vaccination prevented 3,000 P&I deaths (see Table 1). This estimate is similar to estimates of averted P&I deaths during previous seasons (see Table 2). Past comparative data suggest that for the 2015-2016 season the total number of influenza-associated R&C deaths prevented by vaccination may be between two and four times greater than estimates using only P&I deaths (see Table 2).

To calculate these estimates, CDC used 2015-2016 estimates of influenza vaccination coverage (32.2% to 69.7%, depending on age group), vaccine effectiveness (24% to 57%, depending on age group), and influenza hospitalizations rates (20.3 per 100,000 to 321.1 per 100,000, depending on age group and adjusted for influenza testing and test sensitivity).

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2015-2016 Discussion:

During the 2015-2016 season, influenza A (H3N2) viruses circulated early in the season but influenza A (H1N1)pdm09 viruses predominated overall (6). The season was notable because influenza activity peaked in mid-March, 2016; one of the later peaks on record. In the United States influenza activity most commonly peaks between December and February. The overall burden of influenza was substantial with an estimated 25 million influenza illnesses, 11 million influenza-associated medical visits, 310,000 influenza-related hospitalizations, and 12,000 P&I deaths (see Table 3). (Note that past comparative data suggest that the total number of influenza-associated R&C deaths may be between two and four times greater than estimates using only P&I deaths). Overall, the burden estimates for last season are lower than the estimated burden for the three previous seasons, but are near the middle of the range for the previous five seasons (see Table 4).

While influenza seasons can vary in severity, during most seasons people 65 years and older experience the greatest burden of severe influenza disease. This was also true for the 2015-2016 season. While people in this age group accounted for only 15% of the U.S. population, they made up 50% of influenza-associated hospitalizations and 64% of P&I deaths during the 2015-2016 season. Influenza vaccination is the best way to prevent influenza virus infection, and among adults 65 years and older CDC estimates that vaccination prevented 23% of influenza-related hospitalizations during the 2015-2016 season. Vaccine coverage dropped by about 3 percentage points in this age group (to about 63%) between the 2014-2015 and 2015-2016 influenza seasons (7). Such drops in influenza vaccination coverage are costly for older adults, who are at high risk of serious influenza-related complications. If, instead of declining, vaccine coverage had increased by just 5 percentage point in this age group, an additional 36,000 illnesses and more than 3,000 additional hospitalizations could have been prevented during the 2015-2016 season.

The fraction of averted illness from vaccination was lowest among the broader range of working-age adults, aged 18 to 64 years, owing to low vaccination coverage in general in this age group, a drop in vaccine coverage among people 50 to 64 years old, and lower vaccine effectiveness among people 50 to 64 years during the 2015-2016 season (see Table 5). With more than 16 million illnesses from influenza estimated last season and vaccine coverage estimated at 36%, increasing vaccination coverage among persons 18 to 64 years old could have a large impact on reducing illness and work absenteeism. Specifically, if vaccination coverage had increased by 5 percentage points among adults aged 18 to 64 years during the 2015-2016 season, 300,000 additional influenza illnesses and 2,000 additional hospitalizations could have been prevented.

If vaccination rates increased by just 5 percentage points across the entire population, another 500,000 influenza illnesses, 230,000 influenza-associated medical visits, and 6,000 influenza-associated hospitalizations could be prevented. If vaccination rates improved to the Healthy People goal of 70 percent for all age groups, another 2.4 million influenza illnesses and 19,000 influenza-associated hospitalizations could have been prevented. Similarly, improvements to vaccine effectiveness could provide incremental public health benefit.

Strategies to improve vaccine coverage in all ages include ensuring influenza vaccination status is assessed at each heath care encounter during the influenza season (October through May), ensuring that everyone 6 months and older receive a recommendation to get vaccinated and an offer of vaccination from their provider, using standing orders in the health care office, using patient reminder/recall systems aided by immunization information systems, and expanding vaccination access through use of nontraditional settings for vaccination (e.g., pharmacies, workplaces, and schools) to reach persons who might not visit a physician’s office during the influenza season.

Conclusion:

Influenza vaccination during the 2015-2016 influenza season prevented an estimated 5.1 million illnesses, 2.5 million medical visits, 71,000 hospitalizations, and 3,000 P&I deaths. (Note that past comparative data suggest that the total number of influenza-associated R&C deaths prevented by vaccination may be between two and four times greater than estimates using only P&I deaths). Efforts to increase vaccination coverage will further reduce the burden of influenza, especially among working-age adults younger than 65 years, who continue to have the lowest influenza vaccination coverage. This report underscores the benefits of the current vaccination program, but also highlights areas where improvements in vaccine uptake and vaccine effectiveness could deliver even greater benefits to the public’s health.

Although the timing and intensity of influenza virus circulation for the 2016-2017 season cannot be predicted, peak weeks of influenza activity have occurred between December and February during about 75% of seasons over the past 30 years, and significant circulation of influenza viruses can occur as late as May. Therefore, vaccination should be offered to anyone aged ≥6 months by the end of October if possible and for as long as influenza viruses continue to circulate.

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Limitations:

These estimates are subject to several limitations. First, influenza vaccination coverage estimates were derived from reports by survey respondents, not vaccination records, and are subject to recall bias. Second, these coverage estimates are based on telephone surveys with relatively low response rates; nonresponse bias may remain after weighting. Estimates of the number of persons vaccinated based on these survey data have often exceeded the actual number of doses distributed, indicating that coverage estimates used in this report may overestimate the numbers of illnesses and hospitalizations averted by vaccination. Third, this model only calculates outcomes directly averted among persons who were vaccinated. If there is indirect protection from decreased exposure to infectious persons in a partially vaccinated population (i.e., herd immunity), the model would underestimate the number of illnesses and hospitalizations prevented by vaccination. Fourth, vaccine effectiveness among adults 65 years and older might continue to decrease with age, reaching very low levels among the oldest adults who also have the highest rates of influenza vaccination; thus, the model might have overestimated the effect in this group. Fifth, due to data availability, we are unable to estimate influenza-associated R&C deaths for the 2014-2015 or 2015-2016 seasons. P&I deaths are a fraction of all deaths associated with influenza. Based on past studies, (8,9) the total number of R&C deaths associated with influenza that occurred during the 2015-2016 season may be two to four times higher than reported P&I deaths. As data on R&C deaths become available CDC will update estimates of influenza-associated deaths (see CDC Study: Flu Vaccine Saved 40,000 Lives During 9 Year Period).

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Previous Estimates:

Previous estimates of the burden of illness, medical visits, and hospitalizations related to influenza are available online and in scientific publications. (1-5) Estimates using the same methodology as for the 2015-2016 season are shown in the tables below to provide context for the current season’s estimates.

The estimates of P&I deaths related to influenza are a fraction of all deaths related to influenza that occurred a given season. Data on the number of R&C deaths are available with a three-year lag and, therefore, are available for the 2010-2011 through 2013-2014 influenza season. Using these data, CDC estimates that influenza-associated R&C deaths have ranged from a low of 12,000 (during 2011-2012) to a high of 56,000 (during 2012-2013).

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2015-2016 Tables for Influenza Burden and Burden-Averted Estimates:

Table 1: Estimated number and fraction of influenza illnesses, medical visits, hospitalizations, and pneumonia and influenza deaths averted by vaccination, by age group — United States, 2015-2016 influenza season

Age (yrs)		Averted illnesses		Averted medical visits		Averted hospitalizations				Averted pneumonia & influenza deaths*
		No.	95% CI	No.	95% CI	No.	95% CI	Fraction prevented (%)	95% CI	No.	95% CI
6 months-4		980,052	710,239-1,322,705	656,635	474,202-889,804	6,832	4,951-9,221	32.0	27.6-36.9	105	66-156
5-17		1,281,134	940,148-1,733,726	666,190	485,103-908,476	3,513	2,578-4,754	24.2	21.0-27.8	62	42-78
18-49		1,591,114	1,264,333-1,999,398	588,712	465,711-747,321	8,931	7,097-11,223	14.1	12.3-15.7	236	190-285
50-64		743,725	360,432-1,209,238	319,802	153,599-527,189	7,887	3,822-12,824	9.5	4.92-14.3	261	123-423
≥65		487,473	262,848-816,276	272,985	147,356-460,045	44,316	23,895-74,207	22.5	13.5-31.4	2,217	1,167-3,620
All ages		5,083,498	3,538,000-7,081,344	2,504,323	1,725,971-3,532,835	71,479	42,344-112,228	18.9	14.3-24.2	2,882	1,588-4,562

*Only data on pneumonia & influenza deaths are available in real-time during an influenza season; however, these are only a subset of the total deaths associated with influenza, which may be 2 to 4 times higher when other complications are also considered.

Table 2: Estimated number and fraction of influenza illnesses, medical visits, hospitalizations, and pneumonia and influenza deaths averted by vaccination, by season— United States, 2010-11 through 2015-16 influenza seasons

Season	Averted illnesses		Averted medical visits		Averted hospitalizations				Averted deaths
									Pneumonia & influenza deaths*		Respiratory & circulatory deaths†
	No.	95% CI	No.	95% CI	No.	95% CI	Fraction prevented (%)	95% CI	No.	95% CI	No.	95% CI
2010-2011	5,039,277	3,435,322-7,716,921	2,514,353	1,702,599-3,885,779	70,821	33,965-141,708	20.8	13.1-30.3	3,434	1,422-6,906	9,880	3,883- 19,362
2011-2012	1,981,571	1,160,279-3,666,130	968,312	555,687-1,809,753	39,301	17,610-88,885	22.7	13.0-34.0	1,227	505-2,450	3,618	1,400- 6,909
2012-2013	5,628,332	4,235,767-8,327,082	2,701,875	1,997,056-4,085,452	61,522	31,580-162,836	11.1	6.25-19.6	1,823	724-5,517	5,280	2,149- 15,029
2013-2014	6,683,929	5,037,991-8,898,309	3,080,284	2,252,594-4,190,948	86,730	56,447-129,736	21.5	17.2-26.1	3,840	2,298-5,844	9,172	5,267- 14,465
2014-2015	1,606,813	609,744-3,456,741	792,958	296,449-1,744,001	47,449	10,795-144,291	7.5	2.09-15.9	1,419	312-4,255	–	–
2015-2016	5,083,498	3,538,000-7,081,344	2,504,323	1,725,971-3,532,835	71,479	42,344-112,228	18.9	14.3-24.2	2,882	1,588-4,562	–	–

*Only data on pneumonia & influenza deaths are available in real-time during an influenza season; however, these are only a subset of the total deaths associated with influenza that occur each year, which may be 2 to 4 times higher when other complications are also considered.

^†Data on respiratory & circulatory deaths are available with a three-year lag; therefore, estimates on averted respiratory & circulatory deaths are only available through 2013-2014 influenza season at this time.

Table 3: Estimated influenza disease burden, by age group — United States, 2015-2016 influenza season

Age (yrs)	Total population	Estimated illnesses		Estimated medical visits		Estimated hospitalizations			Estimated excess pneumonia & influenza deaths*
		No.	95% CI	No.	95% CI	Hosp. rate (per 100,000)	No.	95% CI	No.	95% Cr I†
<5	19,907,281	2,207,454	1,914,725-2,597,610	1,478,994	1,271,529-1,757,051	77.3	15,389	13,349-18,109	218	163-341
5-17	53,737,830	3,985,210	3,362,617-4,780,978	2,072,309	1,746,545-2,513,438	20.3	10,927	9,220-13,109	193	147-832
18-49	136,800,721	9,717,671	8,434,252-11,413,475	3,595,538	3,069,688-4,288,400	39.9	54,545	47,342-64,064	1,432	1,264-1,659
50-64	63,212,136	6,979,986	6,316,499-7,811,225	3,001,394	2,664,703-3,437,918	117.1	74,021	66,985-82,836	2,439	2,105-2,893
≥65	47,760,852	1,686,841	1,476,732-2,023,024	944,631	814,401-1,141,033	321.1	153,349	134,248-183,911	7,639	6,348-9,404
All ages	321,418,820	24,577,163	21,504,826-28,626,313	11,092,867	9,566,867-13,137,840	95.9	308,232	271,143-362,029	11,995	10,634-13,914

*Only data on pneumonia & influenza deaths are available in real-time during an influenza season; however, these are only a subset of the total deaths associated with influenza that occur each year, which may be 2 to 4 times higher when other complications are also considered.

^†A 95% credible interval (95% Cr I) is provided because of the Monte Carlo approach used to estimate excess pneumonia & influenza deaths.

Table 4: Estimated influenza disease burden, by season — United States, 2010-11 through 2015-16 influenza seasons

Season	Estimated illnesses		Estimated medical visits		Estimated hospitalizations			Estimated excess deaths
								Pneumonia & influenza deaths*		Respiratory & circulatory deaths†
	No.	95% CI	No.	95% Cr I+	Hosp. rate (per 100,000)	No.	95% CI	No.	95% Cr I§	No.	95% Cr I¶
2010-2011	21,096,749	17,582,319-27,698,870	9,956,056	8,187,913-13,224,822	91.2	281,589	239,013-373,931	13,541	12,111-15,372	39,008	34,283-44,986
2011-2012	9,231,004	7,281,179-13,835,345	4,298,616	3,392,861-6,450,996	44.8	139,497	115,865-206,066	4,154	3,691-4,747	12,182	10,638-14,346
2012-2013	35,590,424	30,113,616-44,250,092	16,638,347	13,979,214-20,765,551	188.8	592,688	509,813-733,307	19,962	18,006-22,434	56,102	50,252-63,709
2013-2014	28,445,377	24,968,054-33,040,119	12,613,671	10,942,829-14,817,158	101.9	322,123	283,230-376,646	13,590	12,252-15,307	31,864	27,832-37,234
2014-2015	34,292,299	30,332,937-40,051,029	16,184,354	14,105,043-19,181,789	221.8	707,155	624,149-838,516	19,490	17,718-21,740	–	–
Approximate 5-season range (No.)	9,200,000-35,600,000		4,300,000-16,700,000		140,000-710,000			4,000-20,000		12,000-56,000**
2015-2016	24,577,163	21,504,826-28,626,313	11,092,867	9,566,867-13,137,840	95.9	308,232	271,143-362,029	11,995	10,634-13,914	–	–

*Only data on pneumonia & influenza deaths are available in real-time during an influenza season; however, they are only a subset of the total deaths associated with influenza that occur each year, which may be 2 to 4 times higher when deaths due to other complications are also considered.

^†Data on respiratory & circulatory deaths are available with a three-year lag; therefore, estimates on averted respiratory & circulatory deaths are available for the 2010-2011 through 2013-2014 influenza seasons but not for the 2014-2015 or 2015-2016 seasons.

^§A 95% credible interval (95% Cr I) is provided because of the Monte Carlo approach used to estimate excess pneumonia & influenza deaths.

^¶Range is based on 4 seasons with available data on respiratory & circulatory deaths.

Table 5: Influenza vaccine coverage and vaccine effectiveness, by age group — United States, 2015-2016 influenza season

Age	Vaccine coverage *		Vaccine effectiveness †
	%	95% CI	%	95% CI
6 months-4 years	70	68-71	57	33-72
5-17 years	56	55-57	51	33-64
18-49 years	32	31-33	49	35-60
50-64 years	43	43-44	24	-1-43
≥65 years	63	62-64	41	4-64

*Estimates from FluVaxView. (7)

^†Estimates from US Flu VE Network. (9)

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Questions & Answers:

How does CDC estimate the number of hospitalizations, illnesses, and medically-attended illnesses associated with influenza that occurred in the United States?

Laboratory-confirmed influenza-associated hospitalization rates by age group were obtained from FluSurv-NET, a collaboration between CDC, the Emerging Infections Program Network, and selected state and local health departments in 13 geographically distributed areas in the United States that conduct population-based surveillance. Reported hospitalization rates were adjusted using a multiplier to correct for underreporting, which is calculated from the percent of persons hospitalized with respiratory illness who were tested for influenza and the average sensitivity of influenza testing in surveillance hospitals. These values were measured from data collected during four post-pandemic seasons; data from two seasons were previously reported (2).

Adjusted rates were applied to the U.S. population by age group to calculate the numbers of influenza-associated hospitalizations. The numbers of influenza illnesses were then estimated from hospitalizations based on previously measured ratios that reflect the estimated number of ill persons per hospitalization in each age group (5).

The numbers of persons seeking medical care for influenza were then calculated using age group-specific data on the percentages of persons with a respiratory illness who sought medical care, which were estimated from results of the 2010 Behavioral Risk Factor Surveillance Survey (10).

How does CDC estimate the number of influenza-associated deaths that occurred during the influenza season?

The annual number of excess deaths related to influenza during the season is estimated using a statistical model of weekly deaths that accounts for seasonal trends and indicators for influenza activity and circulation of respiratory syncytial virus (RSV) obtained from viral surveillance activities (11,12). The methods have been previously described elsewhere in detail (13).

Data on deaths were obtained from the US National Center for Health Statistics (NCHS) (11). Data on deaths with pneumonia or influenza listed as a cause of death are available in real-time so can be included in the estimation of burden for the 2015-2016 influenza season; however, previous studies have shown these deaths account for a fraction of all deaths that are related to influenza. Most influenza-related deaths are not due directly to influenza virus infection but are due to secondary bacterial infection or worsening of underlying chronic health conditions, such as chronic heart or lung disease. Even when influenza likely contributed to the events leading to a death, it is often not recognized and rarely listed on the death certificate. Deaths with any respiratory or circulatory (R&C) causes listed on the death certificate are likely more inclusive of deaths related to influenza than P&I deaths; however, data on R&C deaths are not available for up to three years so we are able to calculate annual estimates only for the 2010-2011 through 2013-2014 influenza seasons.

In 2010, CDC estimated the number of influenza-associated P&I deaths and number of influenza-associated deaths with any respiratory or circulatory (R&C) causes listed on the death certificate from 1976-1977 through 2006-2007 influenza seasons (8). From the historical analysis of R&C deaths, we estimate that the total number of influenza-associated deaths that occurred during the influenza season could be two to four times higher than the number of P&I deaths. The current estimate of influenza-associated P&I deaths that occurred during the 2015-2016 season is within the range of P&I mortality estimates from the historical data but roughly half the estimates of influenza-associated R&C deaths.

How does CDC estimate the number of influenza-associated outcomes that were prevented with influenza vaccination?

The annual estimates of influenza vaccination coverage by month during each season and the final end-of-season vaccine effectiveness measurements were used to estimate how many persons were not protected by vaccination during the season and thus were at risk for these outcomes.

The rate of each outcome among persons at risk was then used to estimate the number of influenza-associated outcomes that would have been expected in the same population if no one had been protected by vaccination. Finally, the averted outcomes attributable to vaccination were calculated as the difference between outcomes in the hypothetical unvaccinated population and the observed vaccinated population.

Estimates of 2015-2016 influenza vaccination coverage by month from July 2015 through April 2016, were based on self-report or parental report of vaccination status using data from the National Immunization Survey for children aged 6 months-17 years and Behavioral Risk Factor Surveillance Survey data for adults aged ≥18 years (7).

Vaccine effectiveness estimates for the 2015-2016 season were derived from the US Influenza Vaccine Effectiveness Network, a group of five academic institutions that conduct annual vaccine effectiveness studies (9). The network estimates the effectiveness of vaccination for preventing real-time reverse transcription polymerase chain reaction-positive influenza among persons with acute respiratory illness of ≤7 days duration seen in hospitals, emergency departments, or outpatient clinics in communities in four states.

Calculations were stratified by month of the year to account for annual variations in the timing of disease and vaccination and then summed across the whole season. The prevented fraction was calculated as the number of averted illnesses divided by the total illnesses that would have been expected in an unvaccinated population.

Can you explain the change in the range used to describe influenza-related deaths?

The previous range used to describe influenza-related deaths, from 3,000 to 49,000, was based on data from 30 influenza seasons from 1976 through 2007 (8). The range described in the tables above, 12,000 to 56,000, is based on data from the 2010-2011 through 2013-2014 influenza seasons. Over the past six influenza seasons, the U.S. has experienced several seasons with high rates of hospitalization and severe disease, which may explain why the range over just four seasons has higher numbers of influenza-related deaths than the previously published range.

In addition, other factors may also contribute to why some seasons have different numbers of influenza deaths than seen in the past, including changes in the way that death certificates are filed, changes in the age structure of the population, or changes in the prevalence of chronic medical conditions that put people at high-risk of influenza complications.

How does CDC track flu-related deaths in the United States?

See “Estimating Seasonal Influenza-Associated Deaths in the United States” for the answer to this question.

Why are estimated pediatric deaths in this report different from the number of pediatric deaths reported through the Influenza-Associated Pediatric Mortality Surveillance System?

Deaths associated with laboratory-confirmed influenza in children aged <18 years became nationally notifiable in 2004 and are reported to CDC through the Influenza-Associated Pediatric Mortality Surveillance System. The number of reported deaths is published each week in FluView. However, the number of reported deaths is likely an underestimate of the total number of flu-related pediatric deaths because not all children may be tested for flu or children may be tested later in their illness when seasonal influenza can no longer be detected from respiratory samples.

CDC estimates the numbers of flu-related deaths using statistical models to account for likely under-reporting. The estimates of pneumonia and influenza (P&I) deaths associated with flu in this report are from one such model. Previously published reports have found that the estimated numbers of flu-related deaths in children from statistical models may be two to three times higher than the number of reported deaths. (14)

Can you explain the change in the estimate of influenza-related hospitalizations?

Influenza hospitalizations have always varied from season to season. In the past, CDC had referred to an average number of hospitalizations that was estimated based on records during 1979-2001 from about 500 hospitals across the United States. The average number of people hospitalized was “more than 200,000” but individual seasons over that time period ranged from a low of 157,911 for 1990-1991 to a high of 430,960 for 1997-1998. The new range of 140,000 to 710,000 is based on data from more recent seasons. CDC believes the recent five-year range in this report better represents the variability of influenza seasons than an average estimate.

Can you explain why some of the estimates on this website are different from previously published estimates using this methodology? (For example, total flu-related hospitalization during 2014-2015 was previously estimated to be 974,000, but the current estimate is 707,000 people)?

CDC estimates the burden of influenza using influenza-related hospitalizations and a set of multipliers for the ratio of hospitalizations to cases and the proportion of people who seek clinical care for acute respiratory illness (2). The surveillance system used to estimate influenza-related hospitalizations, FluSurv-NET, collects data on patients hospitalized who have laboratory-confirmed influenza. Influenza testing is done at the request of the clinician, but not everyone is tested. Also, influenza tests are not perfectly accurate. Thus, the reports of laboratory-confirmed influenza-related hospitalizations to FluSurv-NET are likely underestimates of the true number. To adjust for this, we collect data annually from participating FluSurv-NET sites on the amount of influenza testing and the type of test that is used at the site, and this information is used to correct for the underestimate. These testing data are often not available for up to a year after the influenza season, and thus the most recent season’s estimates may need to be revised when more recent data become available, as was the case for the 2014-2015 season.

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References:

1. Kostova D, Reed C, Finelli L, Cheng PY, Gargiullo PM, Shay DK, et al. Influenza Illness and Hospitalizations Averted by Influenza Vaccination in the United States, 2005-2011. PLoS One. 2013;8(6):e66312.
2. Reed C, Chaves SS, Daily Kirley P, Emerson R, Aragon D, Hancock EB, et al. Estimating influenza disease burden from population-based surveillance data in the United States. PLoS One. 2015;10(3):e0118369.
3. Centers for Disease Control and Prevention. Estimated influenza illnesses and hospitalizations averted by influenza vaccination – United States, 2012-13 influenza season. MMWR Morb Mortal Wkly Rep. 2013 Dec 13;62(49):997-1000.
4. Reed C, Kim IK, Singleton JA, Chaves SS, Flannery B, Finelli L, et al. Estimated influenza illnesses and hospitalizations averted by vaccination-United States, 2013-14 influenza season. MMWR Morb Mortal Wkly Rep. 2014 Dec 12;63(49):1151-4.
5. Centers for Disease Control and Prevention. Estimated Influenza Illnesses and Hospitalizations Averted by Vaccination — United States, 2014–15 Influenza Season. 2015 December 10, 2015 [cited 2016 October 27]; Available from: https://www.cdc.gov/flu/about/disease/2014-15.htm
6. Davlin SL, Blanton L, Kniss K, Mustaquim D, Smith S, Kramer N, et al. Influenza Activity – United States, 2015-16 Season and Composition of the 2016-17 Influenza Vaccine. MMWR Morb Mortal Wkly Rep. 2016 Jun 10;65(22):567-75.
7. Centers for Disease Control and Prevention. Flu Vaccination Coverage, United States, 2015–16 Influenza Season. 2016 September 29, 2016 [cited 2016 October 27]; Available from: https://www.cdc.gov/flu/fluvaxview/coverage-1516estimates.htm
8. Centers for Disease Control and Prevention. Estimates of deaths associated with seasonal influenza — United States, 1976-2007. MMWR Morb Mortal Wkly Rep. 2010 Aug 27;59(33):1057-62.
9. Flannery B, Chung J. Influenza Vaccine Effectiveness, Including LAIV vs IIV in Children and Adolescents, US Flu VE Network, 2015–16. Advisory Committee on Immunization Practices; 2016 June 22; Atlanta, GA; 2016.
10. Biggerstaff M, Jhung M, Kamimoto L, Balluz L, Finelli L. Self-reported influenza-like illness and receipt of influenza antiviral drugs during the 2009 pandemic, United States, 2009-2010 [332 Kb, 26 pages]. Am J Public Health. 2012 Oct;102(10):e21-6.
11. Centers for Disease Control and Prevention. Overview of Influenza Surveillance in the United States. 2016 October 13, 2016 [cited 2016 November 1]; Available from: https://www.cdc.gov/flu/weekly/overview.htm
12. Centers for Disease Control and Prevention. The National Respiratory and Enteric Virus Surveillance System (NREVSS). 2016 October 26, 2016 [cited 2016 November 1]; Available from: https://www.cdc.gov/surveillance/nrevss/index.html
13. Foppa IM, Cheng PY, Reynolds SB, Shay DK, Carias C, Bresee JS, et al. Deaths averted by influenza vaccination in the U.S. during the seasons 2005/06 through 2013/14. Vaccine. 2015 Jun 12;33(26):3003-9.
14. Wong KK, Cheng P, Foppa I, Jain S, Fry AM, Finelli L. Estimated paediatric mortality associated with influenza virus infections, United States, 2003-2010. Epidemiol Infect. 2014 May 15:1-8

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Authors

Melissa A. Rolfes, PhD, MPH¹; Ivo M. Foppa, ScD^1,2; Shikha Garg, MD¹; Brendan Flannery, PhD¹; Lynnette Brammer, MPH¹; James A. Singleton, PhD³; Erin Burns, MA¹; Daniel Jernigan, MD¹; Carrie Reed, DSc¹; Sonja J. Olsen, PhD¹; Joseph Bresee, MD¹

¹ Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA
² Battelle Memorial Institute, Atlanta, GA, USA
³ Immunization Services Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA

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Suggested Citation

Rolfes MA, Foppa IM, Garg S, Flannery B, Brammer L, Singleton JA, et al. Estimated Influenza Illnesses, Medical Visits, Hospitalizations, and Deaths Averted by Vaccination in the United States. 2016 Dec 9 [Date Cited]; https://www.cdc.gov/flu/about/disease/2015-16.htm

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