Public health: 71 people need to be vaxxed against influenza to avoid one case

Cochrane Review – this is not encouraging although note it is from 2018 – would like to see more recent data, but still, an NNT of 71 is not good, considering that 71 people have to endure a day or two of side effects to give a little help to one person:

Main results

We found 52 clinical trials of over 80,000 adults. We were unable to determine the impact of bias on about 70% of the included studies due to insufficient reporting of details. Around 15% of the included studies were well designed and conducted. We focused on reporting of results from 25 studies that looked at inactivated vaccines. Injected influenza vaccines probably have a small protective effect against influenza and ILI (moderate-certainty evidence), as 71 people would need to be vaccinated to avoid one influenza case, and 29 would need to be vaccinated to avoid one case of ILI. Vaccination may have little or no appreciable effect on hospitalisations (low-certainty evidence) or number of working days lost.

Vaccines to prevent influenza in healthy adults | Cochrane

This is for last year: Flu Shots Are Moderately Effective This Season, CDC Says (webmd.com)

They are rarely 50% effective: CDC Seasonal Flu Vaccine Effectiveness Studies | Flu Vaccines Work | CDC

For 2024 – 2025: Flu vaccine lowered risk of hospitalization in Southern Hemisphere by 35%: CDC study (msn.com)

and CDC study: Interim Effectiveness Estimates of 2024 Southern Hemisphere Influenza Vaccines in Preventing Influenza-Associated Hospitalization — REVELAC-i Network, Five South American Countries, March–July 2024 | MMWR (cdc.gov)

In five South American countries (Argentina, Brazil, Chile, Paraguay, and Uruguay) the 2024 Southern Hemisphere seasonal influenza vaccine reduced the risk for influenza-associated hospitalization among high-risk groups by 35%. VE might be similar in the Northern Hemisphere if similar A(H3N2) viruses predominate during the 2024–25 influenza season.

It works so well that

To enhance this year’s modest influenza vaccine protection against hospitalization, providers should treat patients with suspected or confirmed influenza as soon as possible with antivirals.

And if I read the notes correctly, this “positive” result for vaccines may have been biased upwards by inclusion of large numbers of children in the sample, and that many of those may have had 2 flu vaccinations (as recommended).

I’ve gotten a flu shot every year but seeing these low efficacies I am not as excited to get a flu shot this year – I’ll probably get one, but uncertain if the benefits are as large as promoted.