International Notes Pertussis -- England and Wales

Pertussis became a notifiable disease in England and Wales in 1940. From 1957 to 1961, following the widespread use of immunization against pertussis, the annual number of cases reported to the Communicable Diseases Surveillance Center (CDSC) declined by approximately two-thirds (Figure 1). However, outbreaks were reported every 3-4 years up to 1974-1975; these outbreaks were substantially smaller than those occurring before the widespread use of pertussis vaccine. From 1967 to 1974, between 76% and 81% of children had completed immunization for pertussis by their second birthdays. Following public controversy about pertussis vaccine reactions, immunization levels dropped dramatically from 77% in 1974 to 30% in 1978. In 1977, reports of pertussis began to increase, culminating in a large outbreak during 1978-1979, the largest since the 1950s. Following this outbreak, vaccination acceptance rose slightly from 30% in 1978 to approximately 45% in 1981. Beginning in 1981, pertussis again reached epidemic levels, and by 1982, the epidemic had become the largest since 1957. In the first 9 months of 1982, 47,508 cases of pertussis were reported. In the third quarter of 1982, reported cases exceeded those in any quarter since the spring of 1957. Over 3,200 cases were reported for the week ending September 10, 1982, alone.

During both the 1977/1979 and the present 1981/1982 outbreaks, reports of Bordetella pertussis isolates received by CDSC followed trends similar to case reports.

Age-specific pertussis incidence rates are shown in Table 1. During the 1970-1975 period, the rate was highest for children under 1 year of age. From 1976 to 1981, following the decline in pertussis immunization acceptance, case reports increased for all age groups. The increase for children under 1 year of age was 2.3-fold; it was 4.4-fold for children age 1-4 years. Incidence rates for 5-9 year olds, some of whom would have been vaccinated before the adverse publicity about pertussis vaccine, increased 1.8-fold.

Pertussis deaths and case-fatality ratios (CFR) are shown in Table 2. From 1955 to 1981, the average annual number of deaths during each 6-year period dropped dramatically. Between 1952 and 1975, the average annual CFR during each 6-year period ranged between 0.11 and 0.13. The average CFR for 1976-1981 decreased to 0.04. Approximately 71% of the deaths from 1952 to 1981 occurred among children less than 1 year old. The average annual CFR for this age group during the same 30-year period was 0.71, about 25 times greater than that of all other ages combined. Reported by Communicable Disease Report, 1982:41, Public Health Laboratory Svc, Communicable Disease Surveillance Center, London, England.

Editorial Note

Editorial Note: During 1977-1979 a major pertussis epidemic with 102,500 reported cases affected all parts of the United Kingdom (1). England and Wales are presently experiencing an even larger epidemic, which began in 1981. Common trends in reported pertussis cases and in B. pertussis isolates confirm the epidemics. Both epidemics followed periods of low vaccine coverage of children. The timing and magnitude of the epidemics, the age group (1-4 years) primarily affected, the fall in levels of vaccine acceptance, and the rise in the number of reported pertussis cases suggest a direct relationship between the decline in vaccination coverage and the occurrence of these epidemics. No other explanations, including socio-economic factors, satisfactorily account for the 1977-1979 epidemic (2-5).

Mortality and CFR during the epidemic periods were low. Most deaths and the highest CFR were among patients less than 1 year of age. Reductions in mortality and in CFR are probably associated with improved care of infants rather than a change in the severity of disease.

Pertussis remains a severe disease for a substantial proportion of affected children. During the 1977-1979 epidemic, 4% of patients reported in 21 health areas of England and Wales were hospitalized and 40% of hospitalized patients were less than 6 months of age (1). Among those hospitalized, 1% required intensive care; one-third of these had complications. Twelve percent of patients with complications had pneumonia, and 5% had convulsions. Applying these figures to the entire population of England and Wales indicates that, during the epidemic, as many as 5,000 children were admitted to hospitals; 2,000 of these were less than 6 months old; 50 required intensive care; 200 developed pneumonia; and 83 had convulsions induced by the disease. In both Glasgow and Edinburgh, extra wards were opened to accommodate children with pertussis.

During the 1977-1979 epidemic, the efficacy of three doses of pertussis vaccine, given as DTP, in preventing pertussis was evaluated among children under 6 years old in one-fourth of the health areas of England (2). Attack rates among DTP recipients and DT recipients were compared. A pertussis vaccine efficacy of greater than 80% was shown for each 1-year-age cohort. When analysis was restricted to bacteriologically confirmed cases, vaccine efficacy was 93%. This study confirmed that the DTP vaccine used in the United Kingdom was highly effective in protecting individuals against pertussis.

The epidemiology of pertussis and the effect, value, and risks of vaccine were reviewed in 1981 by the Joint Committee on Vaccination and Immunization of the Department of Health and Social Security of Great Britain. The Committee concluded that risk from immunization was slight and outweighed by its advantages and that, with due attention to vaccine contraindications, pertussis vaccine should continue to be recommended as part of the basic course of childhood immunization in the United Kingdom (6).

This reassurance and the current major epidemic have led to the recent increase in vaccine acceptance in England. However, acceptance levels are still substantially lower than in 1974, and recent increases are not expected to affect this current outbreak.

The recent epidemics in the United Kingdom have demonstrated that a decline in vaccination coverage in a previously highly vaccinated population can result in epidemics of pertussis. The U.S. Public Health Service Immunization Practices Advisory Committee and the American Academy of Pediatrics, after considering the risks and benefits of pertussis vaccination, continue to recommend routine use of DTP vaccine in the United States (7,8).

References

1. Joint Committee on Vaccination and Immunization. The whooping cough epidemic, 1977-1979. In: Department of Health and Social Security. Whooping cough: reports from the Committee on Safety of Medicine and the Joint Committee on Vaccination and Immunization. London: HMSO, 1981:171-84.

2. Public Health Laboratory Service Epidemiological Research Laboratory. Efficacy of pertussis vaccination in England. Br Med J 1982; 285:357-9.

3. Royal College of General Practitioners, Swansea Research Unit. Effect of a low pertussis vaccination uptake on a large communty. Br Med J 1981;282:23-6

4. Pollard R. Relation between vaccination and notification rates for whooping cough in England and Wales. Lancet 1980;1:1180-2.

5. Miller DL, Alderslade R, Ross EM. Whooping cough and whooping cough vaccine: the risks and benefits debate. Epidemiol Rev 1982;4:1-24.

6. Joint Committee on Vaccination and Immunization. Whooping cough vaccination, 1981. In: Department of Health and Social Security. Whooping cough: reports from the Committee on Safety of Medicine and the Joint Committee on Vaccination and Immunization. London: HMSO, 1981:76-8.

7. ACIP. Diphtheria, tetanus, and pertussis: guidelines for vaccine prophylaxis and other preventive measures. MMWR 1981;30:392-6, 401-7.

8. American Academy of Pediatrics. Report of the Committee on Infections Diseases, 19th ed. Evanston, Illinois: American Academy of Pediatrics, 1982;198-202.

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