Seasonal influenza vaccination and the risk of infection with pandemic influenza: a possible illustration of non-specific temporary immunity following infection

Abstract

Four Canadian studies have suggested that receipt of seasonal influenza vaccine increased the risk of laboratory-confirmed infection with 2009 pandemic influenza A(H1N1). During the influenza season of 2009 in Victoria, Australia, this virus comprised 97% of all circulating influenza viruses for which sub-typing was available. We found no evidence that seasonal influenza vaccine increased the risk of, or provided protection against, infection with the pandemic virus. Ferret experiments have suggested protection against pandemic influenza A(H1N1) 2009 from multiple prior seasonal influenza infections but not from prior seasonal vaccination. Modelling studies suggest that influenza infection leads to heterosubtypic temporary immunity which is initially almost complete. We suggest these observations together can explain the apparent discrepant findings in Canada and Victoria. In Victoria there was no recent prior circulation of seasonal influenza and thus no temporary immunity to pandemic influenza. There was no association of seasonal influenza vaccine with pandemic influenza infection. In Canada seasonal influenza preceded circulation of the pandemic virus. An unvaccinated proportion of the population developed temporary immunity to pandemic influenza from seasonal infection but a proportion of vaccinated members of the population did not get seasonal infection and hence did not develop temporary immunity to pandemic influenza. It may therefore have appeared as if seasonal vaccination increased the risk of infection with pandemic influenza A(H1N1) virus.

Club cells surviving influenza A virus infection induce temporary nonspecific antiviral immunity

“…This phenomenon has been shown experimentally in animal models (1)(2)(3), as well as in humans given the live-attenuated IAV vaccine in clinical studies (4)(5)(6)(7), and has been postulated as a major factor in determining the rate of IAV antigenic drift (8). This temporary immunity has also been observed epidemically when the respiratory syncytial virus season was delayed as a result of the 2009 pandemic IAV outbreak occurring earlier than is normally seen with seasonal strains (9)(10)(11).…”

Respiratory virus transmission dynamics determine timing of asthma exacerbation peaks: Evidence from a population-level model

“…Thus, the recovered class models short-term broad-spectrum immunity against all common cold viruses. Although not fully understood, broad cross-protection after infection has been noted for other respiratory viruses (47,48) and may be mediated by innate immune mechanisms (49,50). Individuals return to the susceptible class after a period of protection, which has duration ω −1 .…”

Partial protection against 2009 pandemic influenza A (H1N1) of seasonal influenza vaccination and related regional factors: Updated systematic review and meta-analyses

“…This mechanism confers a broad protection against infection compared with any other influenza virus when first elicited, but such protection wanes over a short time frame. 17 A Figure 4. Seasonal influenza vaccine against laboratory-confirmed pandemic A (H1N1) influenza infection: Forest plot for subgroup analysis, case-control study.…”

“…Several other studies had studied this issue, but with mixed results. [13][14][15][16][17][18][19] Prior meta-analyses 20 from RCTs or cohort studies cannot provide sufficient data. Thus, results of previous studies were inadequate to draw a definitive conclusion on this issue.…”

“…Moreover, previous experiments on ferret have shown that seasonal influenza infection could protect humans against this pandemic infection. 17 Thus, a subgroup analysis was conducted to investigate further the effect of previous influenza outbreaks on the association between seasonal influenza vaccination and 2009 pandemic infection.…”