What is the vaccine efficacy of repeated influenza vaccinations? (yearly vaccination may reduce its effectiveness)

Circulating viruses, especially influenza A(H3N2) viruses, experience fast antigenic drift that necessitates vaccine reconfiguration. Since vaccination-induced protection against homologous strains may decrease, influenza vaccines must be administered afresh yearly.

In several nations, a yearly seasonal influenza vaccine is currently advised. However, repeated injections of vaccination may reduce its effectiveness.

In the present study, researchers conducted a thorough review and meta-analysis of trials reporting vaccine efficacy by vaccination status from the prior year.

Throughout this systematic review and meta-analysis, the team adhered to PRISMA standards. For publications published between January 1, 2016, and June 13, 2022, the databases MEDLINE, EMBASE, and CINAHL were searched. For research published in English between the beginning of the database and June 13, 2022, the team searched the Web of Science. Additionally, the team looked through reference lists and MEDLINE, EMBASE, and CINAHL Complete databases for non-English language research until December 31, 2015.

Four comparison groups, including vaccinations administered in the present season only, the previous season, the current season and the previous season, and neither season were created. Observational studies and randomized controlled trials that reported vaccine efficacy against laboratory-confirmed influenza were reported. Two reviewers carried out screening, data extraction, and risk of bias analyses separately. Extracted information comprised research, patient characteristics, and odds ratio estimates for each season's vaccination efficacy according to age group and type of influenza virus.

The absolute difference in vaccine efficacy (VE) between those who received vaccinations during the current and prior seasons (VECP) and those who received vaccinations solely during the current season (VEC) was estimated. If inoculated during the current and past seasons and not in the current season, VE more than zero suggests greater vaccine efficacy. By season and age group for each vaccination group, the team calculated pooled vaccine efficacy for influenza A(H1N1), influenza A(H3N2), and influenza B.

According to the majority of estimations, those who received vaccinations during the present season and past seasons had significantly higher vaccine effectiveness than those who received vaccinations solely during the current season.

Estimates of combined vaccine efficacy against influenza A (H3N2) were poor compared to those for other types like A subtypes or B lineages. Vaccine efficacy for the current season only group was 37%, for the current season and the previous season group was 20%; and for the previous season only group was 9%. Except for 2013–14, estimates of the seasonal pooled vaccination effectiveness for the current and prior season groups were lower than those for the current season only group. In both the current and prior season groups, the reduced season-specific pooled vaccine efficacy estimates were most prominent in 2014–15.

The study findings showed that vaccination administered against influenza in two consecutive years offered greater protection as compared to when no vaccine was administered, even though vaccination in the year prior reduces the effectiveness of the vaccine. However, the estimated effects of vaccination received in the prior year are not consistent or severe enough to recommend a different vaccination strategy at this time.

BOL! If you want a headache to go with your what the hell, read this:

The study findings showed that vaccination administered against influenza in two consecutive years offered greater protection as compared to when no vaccine was administered:

Even though vaccination in the year prior reduces the effectiveness of the vaccine. However, the estimated effects of vaccination received in the prior year are not consistent or severe enough to recommend a different vaccination strategy at this time.

21 posted on 10/01/2022 10:59:37 AM PDT by Grampa Dave (Anyone, who can make you believe in absurdities, can make you commit atrocities!!" ~ (Voltaire)!, )

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