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[Seroconversion study of Biken CAM-70 measles vaccine formulations]
L A Camacho1, M S Freire, A M Yamamura
1Departamento de Epidemiologia, Escola Nacional de Saúde Pública, Rio de Janeiro, RJ, Brasil. lcamacho@ensp.fiocruz.br
Insights
Measles vaccine effectiveness varied by viral concentration, with lower doses showing unsatisfactory seroconversion rates. Age also impacted immune response, with younger children exhibiting a reduced immunological response to the Biken CAM-70 measles vaccine.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Measles remains a significant public health concern, necessitating effective vaccination strategies.
- The Biken CAM-70 measles vaccine is widely used, but its optimal viral concentration for inducing robust immunity requires further investigation.
Purpose of the Study:
- To evaluate and compare the seroconversion rates induced by the Biken CAM-70 measles vaccine at varying viral concentrations (5,000, 1,000, and 200 CCID50).
- To assess the impact of vaccine dosage and recipient age on the immunological response to measles vaccination.
Main Methods:
- A randomized, double-blind study involving 223 healthy children aged 9 to 18 months in Rio de Janeiro, Brazil.
- Participants received one of three Biken CAM-70 measles vaccine doses: 5,000, 1,000, or 200 CCID50 (50% Tissue Culture Infective Dose).
- Pre- and post-vaccination antibody levels were measured using the Plaque Reduction Neutralization Test.
Main Results:
- Seroconversion rates were significantly higher in the 5,000 CCID50 group (82%) compared to the 1,000 CCID50 (55%) and 200 CCID50 (37%) groups (p<0.0000).
- Mean post-vaccination antibody concentrations also showed statistically significant differences across the vaccine groups (p<0.000).
- Children aged 10 months or older achieved higher seroconversion rates (73%) than those younger than 10 months (53%).
Conclusions:
- Measles vaccine concentrations below 5,000 CCID50 did not yield satisfactory seroconversion rates in the study population.
- The Biken CAM-70 vaccine's performance was age-dependent, with younger children (especially 9-month-olds) showing a reduced capacity to achieve a full immunological response, consistent with previous findings.
Objectives:
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.