Studies on Measles Vaccination in Nigerian Children

Abstract

In the series of trials reported here, 377 children between the ages of 6 and 20 months were each vaccinated with one of four different batches of live attenuated measles vaccines—4A, 14, 16, or 20—and their responses were compared with those of a further 118 children given poliomyelitis vaccine. The children were allocated to the measles-vaccine or control poliomyelitis-vaccine groups by an effective method of random allocation, and were closely followed up throughout the period when reactions to measles vaccine could be expected. Nearly all the observations were made by a single observer, who was kept unaware of the vaccination status of each child. Pre- and post-vaccination serum samples were taken from an adequate proportion of the children to determine the antibody responses. A further 108 children were given measles vaccine 16 to determine whether the reactions to the vaccine were acceptable to the parents. Two children died during the present series of trials: one of these had been given poliomyelitis vaccine, and the other measles vaccine 20. There was no evidence that vaccination played any part in these deaths. There is a high infant mortality in Ibadan as elsewhere in West Africa, available figures indicating a mortality rate of approximately 1% per month in the age-group we were studying (McGregor et al., 1961 ; H. Gillies, personal communication, 1963). In the comparative trials it was found that vaccine 20 produced much milder reactions than did any of the other vaccines tested. In the majority of cases children given this vaccine developed a mild febrile response ranging up to 101.5° F. (38.6° C.) (rectal) which lasted for approximately two days. In other respects they did not differ from children given poliomyelitis vaccine, with the exception that when infections of the upper respiratory tract were prevalent those given the measles vaccine tended to develop follicular tonsillitis, while children given poliomyelitis vaccine more often developed only a mild pharyngitis. It is noteworthy that in the acceptability trial using vaccine 16, which causes more severe reactions than does vaccine 20, 83% of one group of mothers and 65% of another regarded the vaccine as acceptable. Despite the high level of attenuation of vaccine 20, it was found to result in the production of neutralizing antibodies in 93% of initially non-immune recipients. We consider that vaccine at this level of attenuation is suitable for use on a larger scale than we have undertaken to date. © 1964, British Medical Journal Publishing Group. All rights reserved.