Posted on behalf of Dr Thomas Cherian, with many thanks for the response.
Several different combination vaccines are licensed for use in infants. These contain various combinations for diphtheria, tetanus, Hib, hepatitis B, IPV and pertussis vaccines (some contain acellular pertussis and others whole cell pertussis vaccines). Many of these combinations are also prequalified by WHO. All the combination vaccines that are licensed by regulatory agencies that are fully functional and are pre-qualified by WHO are safe and effective; comparison of safety and efficacy of the combination against vaccines administered individually is part of the assessment process for licensure. We are not aware of a combination vaccine that includes PCV in the above mix. Perhaps you are mistaken about that.
Combination vaccines have several advantages in that they reduce the number of immunization clinic visits, the number of injections required by the child, improved compliance and, thereby, higher coverage. Some studies have shown that some of the combination vaccines have a higher rate of local reactions (local pain and redness) than when the vaccines are administered separately. In the subset of studies that used combinations with whole cell pertussis vaccine, this did not seem to be the case and the increased rate of local reactions did not reach statistical significance.
While there have been reports of deaths following the use of combination vaccines, in no instance have these been found to be causally linked. In Sri Lanka, the national programme did temporarily suspend the use of pentavalent vaccine, but they continued to monitor deaths following vaccination. The rates observed when they reverted to tetravalent vaccine were no different from those observed following the pentavalent vaccine, indicating that these represented coincidental child deaths that were only temporally related to administration of the vaccine dose. All the countries referred to in the articles “India Serves Up Costly Cocktail of Vaccines” are currently using the pentavalent vaccine, as are over 170 countries worldwide.
WHO policy recommendations do aim to maximize population benefit, but not at the expense of safety, which in all cases remains paramount. Wherever there are areas of uncertainty, the WHO position papers do clearly lay these out.
While I fully agree with Prabir that each family needs to be fully informed and make decisions based on their social situation, there are a few inaccuracies in his response that deserve comment. The increase in reports of AEFI following the pentavalent vaccines in a few countries, as compared to quadrivalent vaccines, is more likely related to the fact that AEFI monitoring processes were concomitantly strengthened in those countries. As indicated above, further investigation in Sri Lanka revealed that the AEFI rates remained the same when they suspended the use of pentavalent vaccines and reverted to using tetravalent vaccines.
Prabir’s response also seems to imply that rotavirus disease is less common in populations where there is access to safe water. In fact, this is not true. Rotavirus is a “democratic virus” equally prevalent in communities with and without access to safe water. Rotavirus is more often transmitted through contact than through contaminated water. It is also not true that those coming to Asia from the West are naive and, therefore, more likely to suffer from severe rotavirus diarrhoea. In fact, the reverse is true. The incidence of severe rotavirus diarrhoea is much higher in high child mortality populations, which is why the vaccine is likely to have greater benefits despite lower vaccine efficacy. In addition, data from Vellore, where Prabir trained, show that urban Indian children are more likely to suffer from severe rotavirus diarrhoea following second or subsequent infection whereas in the West severe disease mainly occurs with the first episode of infection.
It is also a misconception that pneumococcal pneumonia occurs more commonly in colder climes. In fact, the reverse is true. Available evidence through well conducted studies show that the incidence of invasive pneumococcal disease and pneumococcal pneumonia are higher in developing countries (
http://www.who.int/immunization_monitoring/burden/Pneumo_hib_estimates_2000/en/index2.html). While it is true the pneumococcal pneumonia can easily be treated with antibiotics, timely access to antibiotics is low in most developing countries. Even if pneumonia can be treated with antibiotics, vaccines reduce unnecessary pain, suffering, and the longer-term consequences to the child by preventing pneumonia. Well-to-do parents also would much rather their child does not develop pneumonia, than wait to treat if pneumonia develops.
Dr. Thomas Cherian
Department of Immunization, Vaccines and Biologicals
World Health Organization