The response to oral poliovaccine in persons aged 16–18 years

Abstract

SUMMARY: Serum neutralizing antibodies to polioviruses were titrated in serum samples from 182 police cadets aged 16–18 years before and, in 168 of the cadets, 6 weeks after vaccination with a single dose of oral polio vaccine (OPV). Faecal excretion of poliovirus was also followed. Vaccination histories were obtained and confirmed whenever possible.Pre-vaccination antibody could not be detected against type 1 in 9·3% cadets, against type 2 in 2·7% and against type 3 in 7·7%. Absence of antibody to at least one virus type was found in 14·3 % of the cadets.In 93 cadets in whom vaccination histories could be confirmed 40 had received only inactivated polio vaccine (IPV) previously; of these 23% lacked antibody to at least one virus type, and they had less intestinal immunity to a challenge dose of OPV than those previously given OPV. Only two of the cadets known to have had OPV were non-immune – both had received a single dose following full courses of IPV. However, cadets who had received OPV had their last dose of vaccine more recently (average 4.6 years) than those who had received only IPV (all 12 years or more).The serum antibody response to a single booster dose of OPV, and the faecal excretion of each type of virus after vaccination, showed an inverse relation to the corresponding pre-vaccination antibody concentration. A single dose of OPV did not reliably boost the immunity of those who possessed adequate immunity, and a failure to respond was also observed in a proportion of the cadets with no detectable antibody, mostly in the case of type 3 antibody and particularly if antibody to types 1 or 2 virus was also absent. No evidence was obtained that intestinal immunity could be expected in the absence of detectable circulating antibody.The reasons for the absence of a serological response to OPV in some subjects are discussed and consideration is given to the practical significance of the findings. It is suggested that reinforcement of polio immunity at school-leaving is important, particularly at the present time when many of those aged 16–18 years will have been vaccinated only with IPV. A single does of OPV is not ideal for this purpose, not only because a small proportion of persons are liable to be left unprotected, but also because failure to produce a reliable boost in persons with adequate immunity at the time of vaccination gives rise to the possibility that they may become susceptible later in adult life.