[Seroconversion study of Biken CAM-70 measles vaccine formulations].
OBJECTIVE
To compare seroconversion rates induced by Biken CAM-70 measles vaccines at different viral concentrations.


METHODS
Healthy children aged 9 to 18 months from a primary health care unit in Rio de Janeiro, Brazil, and whose guardians agreed with their participation, were randomly assigned to receive one of the following vaccine formulations: 5,000, 1,000 or 200 CCID50 (50% Tissue Culture Infective Dose). The research team, participants, and data analysts were blinded to the type of vaccine administered. Pre- and post-vaccination antibody levels were assessed through Plaque Reduction Neutralization Test. Two interim data analyses were planned to assess unequivocal evidence of the superiority of one of the vaccine types.


RESULTS
From 223 recruited children, 84% completed the whole course. Of them, 79% were less than 10 months of age, and 93% did not show detectable measles antibodies in pre-vaccination serum. Seroconversion (four-fold increase in antibody levels) in groups vaccinated with 5,000, 1,000 or 200 CCID50, were 82%, 55%, and 37% (p<0.0000), respectively. Differences in the mean concentration of post-vaccination antibodies were also substantial and statistically significant (p<0.000). Seroconversion rates (pooling data from all vaccine formulations) were 73% to children aged 10 months or more, and 53% in those below 10 months.


CONCLUSIONS
Vaccines with concentrations below 5,000 CCID50 did not produce satisfactory seroconversion rates. The vaccine performance by age was consistent with that seen in other studies using Biken CAM-70 strain in which a sizable proportion of 9-month-old children failed to achieve full immunological response.
Camacho
L A
LA
Departamento de Epidemiologia, Escola Nacional de Saúde Pública, Rio de Janeiro, RJ, Brasil. lcamacho@ensp.fiocruz.br
Freire
M S
MS
Yamamura
A M
AM
da Luz Leal
M
M
Mann
G
G
D000704:Analysis of Variance; D000914:Antibodies, Viral / Q000097:blood; D004339:Drug Compounding; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008457:Measles / Q000276:immunology / Q000517:prevention & control*; D008458:Measles Vaccine / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology*; D012107:Research Design; D012698:Serologic Tests
D000914:Antibodies, Viral; D008458:Measles Vaccine