The pertussis (whooping cough) vaccine may not prevent transmission of the disease and infants aged 0-2 months are most at risk.
This is according to data from the Public Health Laboratory Service Communicable Disease Surveillance Centre in London.
The Centre admits that, while the overall trend in whooping cough in a downward one, there has been an increase in undetected transmission.
This increase is most evident in infants under three months of age and is likely to be the result of coming into contact with older, vaccinated but unprotected people.
If this is true, then it kicks away two of vaccination's main platforms namely, that vaccinations are effective over a lifetime and that herd immunity will protect those who are, for whatever reason, unvaccinated (Lancet, 2000; 355: 1553-4).