Malaria vaccine in children under 12 months of age [letter]
1995
A pilot case control study of the SPf66 malaria vaccine in infants in Gambia revealed that the infants receiving the vaccine had more episodes of clinical malaria than those not receiving the vaccine (18 vs. 4 episodes after 2 doses during the first malaria season; 86 vs. 26 episodes after 3 doses during the next season). Regardless of season the difference in episodes between the cases and controls was highest for the 25 infants who received the high-dose Colombian preparation the most immunogenic preparation. These findings suggest that the immune response in infants is different than that of older children such as those in Tanzania who experienced a strong increase in antibody titers after receiving the SPf66 vaccine. In the pilot study the second and third doses of the vaccine had been administered to the infants before and after the peak malaria transmission season. The researchers and members of steering and ethics committees debated whether or not the third dose should be administered to children in the main field trial. The result being that children in the main field trial received all three doses all of which were administered during the season of low malaria transmission. Clinical malaria did not increase in the cases in the main field trial. Further in both cases and controls the rate of severe malaria and mortality was very low. Errors in study planning done by the investigators and the steering and ethics committees caused the dilemma presented during the main field trial. The pilot study was essentially a phase I study which should have been designed to detect any possible serious adverse effects. Thus it was also primarily a safety study. The study was not designed to assess the possibility of the development of an abnormal immune response to malaria in immunologically immature infants however. In addition the infants received the vaccine during the peak season of transmission while the children in the main trial received it during the low malaria season. Data from the pilot trial especially safety data were not necessarily relevant to the main trial. Disruption of the natural immunity in infants would be disastrous.
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