Measles virus haemagglutination-inhibition antibodies among pregnant and non-pregnant women in the vaccine era in Harare, Zimbabwe.

OBJECTIVES: To determine the prevalence of measles virus haemagglutination-inhibitive antibodies among pregnant and non-pregnant women born before 1963 (pre-vaccine era) and those born after 1963 (vaccine era) in Harare.

DESIGN: Prospective study of serum samples collected from pregnant and non-pregnant women born during the pre-vaccine era and vaccine era in Harare.

SETTING: A laboratory based study at the Virology Laboratory, Department of Medical Microbiology, University of Zimbabwe using serum samples of women from different communities in Harare.

SUBJECTS: 546 pregnant and non-pregnant women.

MAIN OUTCOME MEASURES: Age, pregnant or not pregnant and the use of measles virus haemagglutination-inhibition antibody tests to determine prevalence rates or levels of antibodies to the measles virus.

RESULTS: The results showed that 158 (28.9pc) out of a total of 546 pregnant and non-pregnant women screened were positive for measles virus haemagglutination-inhibition antibodies (MVHIA) at titers ranging from 1:10 to 1:80.39.8pc and 18pc of pregnant women born before 1963 and after 1963 were respectively positive whereas 49pc and 27.3pc of non-pregnant women born before 1963 and after 1963 were also positive for MVHIA respectively. The mean age of women born before 1963 was 38 + 2 years (range 34 to 60 years, median 42 years) while those born after 1963 had a mean age of 22 + 2 years (range 10 to 28 years; median 23 years). Higher antibody titers (1:40 and 1:80) were most commonly observed in both pregnant and non-pregnant women born during the pre-vaccine era than those born during the vaccine era and the difference was of statistical significance (p < 0.01).

CONCLUSION: Finally results suggest that immunity acquired by exposure to wild measles virus (pre-vaccine era or natural immunity) is higher than immunity acquired following immunisation (vaccine era) and this may affect the duration of maternally derived immunity by children of mothers born during the different eras. Consequently, while we expect that this finding will be of value in immunisation schedules, we suggest a titer of 1:40 and above as the likely screening titer for routine identification of protected women in Zimbabwe.