Q: Assuming that the World Health Organisation monitors the safety, effectiveness and impact of a vaccine before it is introduced into the national immunisation programme of any country, can you provide some information on the observations during the clinical trials of the pentavalent vaccine with regard to its safety and efficacy?
A: WHO’s vaccine prequalification programme serves to ensure that all countries have access to vaccines that meet international standards of quality, safety and efficacy and are appropriate for the target population. WHO, therefore, believes all prequalifed pentavalent vaccines to be safe and effective.
As with all vaccines, however, reactions following administration can occur. The most common reactions observed following use of pentavalent vaccine include moderate inflammation at the site of injection and transient fever in a small proportion of cases. Serious reactions are extremely rare, with anaphylaxis (a form of general allergic reaction that most often evolves favourably) observed in less than one case per million.
This very low risk should be weighed against the lives saved through the protection provided by the pentavalent vaccine against five diseases: diphtheria, tetanus, pertussis (whooping cough), hepatitis B, and haemophilus influenza type b (Hib).
Q: Are the Hb and Hib vaccines taking a piggy backride on the DPT? How would you react to the allegations raised from certain quarters that it is merely a marketing trick? Would the Hib vaccines be more effective if given separately and does it in anyway lower the effectiveness of other vaccines when given in combination?
A: Hepatitis B and Hib vaccines provide safe and effective protection against two germs responsible for extremely serious diseases. WHO recommends their use in all countries for all infants. The combined administration with DTP is a way of minimizing the number of injections that are required for infants.
Administering hepatitis B and Hib vaccines together with DTP does not appear to lower the effectiveness of DTP.
Q: Is it true that the pentavalent vaccine that was introduced in the national immunisation programme in Sri Lanka in January 2008 had to be withdrawn after several thousand doses were administered as there were 25 serious adverse reactions, including five deaths? What was the finding of the WHO expert panel that investigated the case?
A: Authorities in Sri Lanka suspended the use of a pentavalent vaccine (Quinvaxem) in 2008 as a precaution following notification of serious adverse events by the national immunization programme.
The investigation of the cases, conducted with the assistance of WHO, did not identify conclusive evidence for a causal relationship between the administration of the vaccine and the adverse events. Sri Lanka has since resumed the use of pentavalent vaccine.
Q: Similarly, it was reported that the pentavalent vaccine introduced in the national immunisation programme of Bhutan in July 2009 was withdrawn within two months and after eight deaths. If the deaths were not related to immunisation, why was the entire batch of vaccines recalled?
A: Authorities in Bhutan suspended the use of a pentavalent vaccine (Easyfive) in 2009 as a precaution following notification of serious adverse events.
This decision was taken as a precautionary measure although there was no evidence of a causal relationship between the vaccine and the adverse events.
No conclusive evidence was found to incriminate the vaccine. Bhutan has since resumed the use of pentavalent vaccine. No recall of the batches involved was required.