Prevention of rubella infection among women of child-bearing age by screening and vaccination. Assessment during a nationwide rubella epidemic in Israel

Leffe r Prevention of rubella infection among women of child-bearing age by screening and vaccination. Assessment during a nationwide rubella epidemic in Israel Sir, The conclusions of a recent symposium on prevention of congenital rubella infection emphasized the basic differences in the impact of two main immunization strategies on the incidence of congenital rubella I. One strategy, adopted by US authorities and based on mass vaccination of children, resulted in a significant decrease of both acquired rubella and congenital infection. By contrast, selective immunization of the female population introduced in UK, Israel and other countries had not thus far had an effect on either of these parameters of rubella epidemiology. We had the opportunity to perform a large field trial with the RA-27/3 rubella vaccine in communal settlements in Israel during the years 1974-1975. Follow-up performed during and after a nation-wide rubella epidemic in 1979 provided valuable information concerning the protection of women of childbearing age by screening and vaccination. A voluntary programme of screening for rubella antibodies was initiated by the Division of Laboratories of the Ministry of Health in 1974. It had been planned to include the total child-bearing female population (~15 O/)(/ sub-

jects) of all 250 communal settlements. Sera were screened for rubella antibodies by the haemagglutination-inhibition (HI) test as previously described 2. Rubella vaccine, RA-27/3 strain 3, purchased from Burroughs-Wellcome Laboratories was offered to all seronegative women (HI <1:16). In 1979 a nationwide rubella epidemic swept the country. The morbidity among women in child-bearing age reached 4.7% 4. The protection provided by vaccination in communal settlements was assessed through a questionnaire, which included data on screening and vaccination as well as morbidity during the epidemic. Only 70 settlements answered the questionnaire and of these 53 were affected by the epidemic as documented by serologically confirmed rubella cases. Of 4412 female members of these settlements, 3299 (75'70) were screened for rubella antibodies in 1974-1975 and 564 (17%) were classified as seronegatives. Of these seronegatives, 441 (78%) were vaccinated following screening. Rubella morbidity during the epidemic among vaccinated and unvaccinated women is summarized in the table. The control, unvaccinated group of 312 women included both 123 known

seronegatives who escaped vaccination and 189 estimated seronegatives (17%) of 1113 women who did not submit blood samples for screening. As a similar morbidity was observed in both groups (27.5 and 3(l.8%, respectively), the data were combined, giving a mean incidence in the unvaccinated group of 28.8%. In contrast, only two cases of clinical rubella were observed among 441 vaccinated women (incidence (l.4% and vaccination efficacy 98.6%). These results, in our opinion, provide strong evidence in favour of selective vaccination of child-bearing women for prevention of congenital rubella infection. A. Fogel, Ch.B. Geriehter and B. Barnea

Central Virology Laboratory, Ministry of Health, The ('haim Sheba Medical Center, TeI-Hashomer, Israel

References 1

2

3 Clinical rubella among women of child-bearing age in communal settlements in 1979

Group

No. of seronegatives

Vaccination in 1975

1 2

312 441

No Yes

0264--410X/87/020082-01 $03.00 (~) 1987 Butterworth & Co. (Publishers) Ltd.

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V a c c i n e , Vol. 5, J u n e 1987

Cases of rubella No.

%

Vaccine efficacy (%)

90 2

28.8 0.4

98.6

4

Hinman, A.R. Prevention of congenital rubella infection: Symposium summary. Rev. Infect. Dis. 1985, 7, 5212-5215 Fogel, A., Gerichter, Ch.B., Rannon, L., Berenholtz, B. and Handsher, R. Serologic studies in 11 460 pregnant women during the 1972 rubella epidemic in Israel. Am. J. Epidemiol. 1976, 103, 51-59 Ptotkin, S.A., Farquhar, J.D., Katz, M. and Buser, F. Attenuation of RA27/3 rubella virus in WI-38 human diploid ceils. Am. J. Dis. Child. 1969, 118, 178-185 Fogel, A., Handsher, R. and Barnea, B. Subclinical rubella in pregnancy - occurrence and outcome. Isr. J. Med. Sci. 1985, 21, 133-138