Further studies with quadruple vaccine

Reactions to the pertussis component of the original commercial batches of quadruple vaccine against poliomyelitis, diphtheria, tetanus and pertussis (Quadrilin, Glaxo Laboratories) gave some cause for concern. Severe reactions were found to be more common in infants under 6 months of age than in older infants. A modified quadruple vaccine, which has been used in N. Ireland since October 1964, was found to give rise to significantly fewer and milder reactions. This vaccine when given in three doses separated by intervals of 6–9 weeks and 6 months to fifty-eight infants most of whom were 6–7 months of age at the start of immunization was found to give a satisfactory immunological response.