The effect of cigarette smoking on susceptibility to epidemic influenza and on serological responses to live attenuated and killed subunit influenza vaccines.

The effects of cigarette smoking on the incidence of epidemic influenza and on the serological response to influenza vaccination with killed subunit and live attenuated vaccines have been investigated during comparative vaccine trials in Western Australia. It was found that cigarette smokers with no pre-epidemic haemagglutination-inhibiting (HI) antibody (titres of less than or equal to 12) were significantly more susceptible to epidemic influenza than non-smokers. Smokers were no more susceptible however, if they had possessed detectable pre-epidemic HI antibody. A significantly higher proportion of smokers sero-converted after receiving the live virus vaccine than their non-smoking counterparts, but this could not be correlated with pre-vaccination HI antibody titres. The longevity of the immune response to the subunit vaccine was severely depressed 50 weeks post-vaccination in smokers who had possessed little or no immunity before vaccination (titres of less than or equal to 12). This antiboyd deficit was not observed in live virus vaccines or subunit vaccinees with pre-vaccination HI antibody (titres of greater than or equal to 24). Post-vaccinal symptoms were similar regardless of vaccine group or smoking history.