, according to a new study.
That information may be useful in deciding the impact of vaccination programs that use a combination of maternal and infant vaccines and consider schedules with a delayed start, saidof the University of Oxford (England) and her associates.
In this study, 5,097 children in 16 cohorts from 13 countries had pneumococcal antibody concentrations assessed from blood samples taken before their first dose of vaccine, and 2,925 infants from 5 cohorts in 4 countries had meningococcal antibody concentrations available.
At the time of their first vaccination, the children were ages 5-23 weeks and were from countries in Europe, Africa, Latin America, and South and East Asia. These populations have no routine programs of immunization in pregnancy, the researchers said. So, the maternal antibodies are passively acquired, and the decay rates may differ from those induced by maternal vaccinations.
The seroprevalence of maternal antibodies in infants was 92% for pneumococcal serotype 14 and 80% for serotype 19F; it was 30% for serotype 4 and 34% for serotype 1. Thirteen percent of infants had detectable levels of group C meningococcal antibodies prior to vaccination, and 43% had group A antibodies.
For the pneumococcal antibodies, “there was statistically significant variation in half-life estimates between country cohorts and between serotypes (both P less than .0001),” the researchers said. The half-life estimate was lowest – at 39 days – for serotype 6B, and highest – at 48 days – for serotype 5. The overall estimate across serotypes was 43 days.
“The age of the child was not significantly associated with decay rates (P = .103), confirming the assumption of exponential decay,” they said.
For the meningococcal antibodies, the half-lives were 43 days for group A and 40 days for group C.
“Substantial proportions of infants have antibodies to many vaccine serotypes of pneumococcus at the age when a vaccine program might normally commence,” the investigators noted. “Conversely, antibodies against capsular groups A and C meningococcal polysaccharides were less common, particularly for group C, which was only present in 13% of infants in the four countries contained in this analysis.
“Higher levels of group A meningococcal antibodies than group C have also been seen in unvaccinated adults of childbearing age in the Netherlands, and in mothers in the United Kingdom,” the researchers added. “Passively acquired maternal antibody has been shown to adversely affect the magnitude of the immune response to vaccination with pneumococcal conjugate vaccine, and increase the occurrence of otitis media in infants under 6 months of age.”
The proportion of infants who had maternal antipneumococcal antibodies differed between serotypes, the authors noted. Almost all infants had serotype 14 pneumococcal antibodies, and very high proportions of infants had serotype 19F antibodies.
“We have previously shown that the antibody response to vaccination with pneumococcal conjugate vaccine is adversely affected by the presence of maternal antibody,” the investigators said. “This inhibitory effect is greatest for serotype 14, with children seropositive from maternal antibodies having a response to vaccination that is only three-quarters the magnitude of those with no maternal antibody.”
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