Finland was the first country to provide the Seqirus-made avian influenza A(H5N8) vaccine to people in high-risk jobs after the large H5N1 outbreak in 2023 that affected wild birds and fur farms. A recent study in Nature Microbiology demonstrates the vaccine's efficacy and provides lessons for worldwide preparedness. 

The MF59-adjuvanted vaccination elicited significant immune responses from research participants. After two doses, most previously unvaccinated people had seroprotective antibody levels, which means their blood had adequate antibodies to fight infection. In one test, the seroprotection rate was 83%, while in another it was 97%. Surprisingly, the antibodies identified other H5 strains responsible for epidemics in Europe and the United States.

"According to the authors, these results show that getting two doses of the vaccine creates strong immune responses that should help protect against the H5 viruses currently spreading." 

T-cell responses, which help the body remember and fight infections, increased five times after the second dose, showing that protection is stronger and lasts longer. Surprisingly, participants who had previously gotten H5 vaccines years or even a decade ago responded quickly to a single current dosage, with high antibody levels and no benefit from a subsequent dose. This suggests robust immune memory and the possibility of quick protection if epidemics escalate. 

Despite the vaccine's scientific promise, acceptance among high-risk groups was surprisingly low. The vaccination was administered to fewer than 10% of eligible individuals, including fur farm workers, veterinarians, laboratory professionals, bird ringers, and poultry workers. Despite intensive outreach, none of the most vulnerable groups, fur farm workers, took part. Limited access, limited awareness, concern about personal risk, and a lack of preceding human data all likely contributed to reticence. 

"Even if a vaccine is highly immunogenic and well matched to circulating viruses, it can only protect those who receive it," the study's authors stated. 

The Finnish experience demonstrates an important public health lesson: powerful vaccinations alone are insufficient. Proactive participation, clear communication, and easy access are critical for protecting the most vulnerable. Priming at-risk populations today may enable rapid boosting with future vaccines if H5 outbreaks spread globally, providing timely and substantial protection even if the booster is not a perfect match.