No abstract

SUMMARYThe single radial haemolysis (SRH)

SUMMARYOne hundred and nineteen volunteers were divided into five groups, and each volunteer inoculated subcutaneously with an aqueous subunit B/Hong Kong/73 vaccine containing 40, 20, 10, or 5 ,ug of HA or saline alone in a 0-5 ml volume. The incidence of reactions was recorded 24 h after inoculation. One month following immunization the serum HI antibody to B/Hong Kong/73 virus was measured; each volunteer was inoculated intranasally with live, attenuated influenza B (RB77) virus; and the incidence of infection by the challenge virus was determined by HI antibody response.The results showed that the incidence of reactions to all doses of vaccine were relatively low, the severity mild, and the duration short. However, the incidence of reactions was highest for those given 40 jug HA and least for those given 5 4g HA. The serum HI antibody responses to vaccine showed a dose-response relationship. For volunteers given 40 jug HA, 22 (96 %) showed a fourfold rise in antibody titre and all volunteers had antibody titres of > 40 following immunization: for volunteers given 5 ,ug HA the g.m.t. increased from 16-6 to 86-1; and for those given 10 and 20,sg HA the response was intermediate. Following challenge, the lowest incidence ofinfection was seen in volunteers given the highest dose of vaccine. However, all doses of vaccine induced some protection against challenge virus infection, and the incidence of infection was directly related to the serum antibody titre at the time of challenge. The 50 % protection titre of serum HI antibody was estimated as 15 to 20.

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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 dose 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.