Vaccination in the control of influenza. Interim report to the Director of the Public Health Laboratory Service on a Collaborative Study with the Post Office

Active synthesis of hemagglutinin-specific immunoglobulin A by lung cells of mice that were immunized intragastrically with inactivated influenza virus vaccine

Intragastric inoculation with whole-virion vaccine of inactivated influenza virus resulted in production of hemagglutinin (HA)-specific immunoglobulin A (IgA) and IgG both in lung lavage fluids and in serum samples of mice. HA-specific IgA was the predominant isotypic antibody secreted in the lung lavage fluids (average IgA/IgG ratio, 13:1), whereas HA-specific IgG was the major antibody class in serum (average IgA/IgG ratio, 0.3:1). These responses were similar to the antibody responses stimulated by intranasal infection with live influenza virus. In vitro cultures of lymphoid cells from lungs and Peyer's patches, but not from spleens, in the presence of homologous antigen, from mice vaccinated intragastrically synthesized mostly HA-specific IgA. Mice immunized parenterally with inactivated influenza virus produced only IgG in lung lavage fluids and sera. Cultures of lymphoid cells from their spleens, but not their lungs, synthesized HA-specific IgG upon antigenic stimulation in vitro; neither synthesized IgA. These in vitro cell culture results, as well as the inverse relationship of IgA/IgG ratios in lung lavage fluids and sera, demonstrated that the IgA antibody in lung lavage fluids was actively synthesized locally in the lungs of intragastrically immunized mice. This finding was consistent with the migratory distribution of antigen-primed lymphoid cells from Peyer's patches to distant lymphoid tissue such as lung. Intragastric vaccination conferred protection against intranasal challenge with a lethal dose of virulent virus.

Vaccination against influenza: a five-year study in the Post Office

An injection of influenza vaccine was offered to approximately 60 000 Postal and Telecommunications staff at the beginning of five successive winters. The sickness absence of this group, which included those who accepted the offer of vaccine as well as those who did not, was compared throughout the winter with that of a similar number of employees who were not offered vaccine. The two groups, ;vaccinated' and control, comprised the staff of nearly 400 Post Office units scattered throughout Great Britain, the units of the two groups being matched as far as practicable for numbers employed, type of work, region and type of location.The proportion who accepted vaccine fell from 42% in the first year (when only 26 000 Telecommunications employees were offered vaccine) to 35% in the second year, and 25% by the fifth year.With the exception of Telecommunications employees in 1972-73, the sickness absence rate of the group offered vaccine was less than that of the group not offered vaccine, and the difference was evident during the winter observation periods both when influenza was prevalent and when it was not. In the last four years of the study the average difference in sickness absence between the ;vaccinated' and control groups was 1.26 days per 100 employees per week during and 1.12 days outside the influenza periods. Moreover, the difference during the influenza periods was greater than could be expected from the acceptance rate of vaccine and the estimated attack rate of influenza. The apparent reduction in sickness absence of the group offered vaccine in comparison with the group not offered vaccine represented an appreciable saving in cost.It is suggested than an annual influenza vaccination campaign in industry may produce financial benefit, but that only a proportion of the benefit is due to an improvement in health.

Vaccination in the control of influenza

Although killed influenza vaccine given by injection is protective, able to reduce sickness absence in industry and to control influenza in the armed forces, it has not so far been possible to demonstrate more than a small effect on the disease in otherwise healthy adults in industry and offices in the United Kingdom. The reasons are probably the poor rate of acceptance of vaccine, the relatively low incidence of clinical influenza in most years, and the incomplete protection given by the vaccine. Until major epidemics can be accurately forecast it is suggested that influenza vaccination may most usefully be used on a selective basis, namely for protecting those with illness predisposing to a severe effect from influenza; persons in institutions such as schools and homes for the elderly; key workers in the general population; and persons over the age of 65 years among whom considerable mortality occurs in winters when influenza is prevalent.