Experts published their findings on 19/11 in the New England Journal of Medicine. The nucleoside-modified messenger RNA (modRNA) influenza vaccine demonstrated promising immunogenicity against influenza and an acceptable safety profile in phase 1-2 trials. The experimental shot, tested on over 18,000 adults aged 18-64 during the 2022-2023 flu season, showed higher efficacy than conventional vaccines.

However, the mRNA vaccine had a higher rate of side effects. Around 70% of recipients experienced injection site pain, swelling, and redness, compared to 43% in the traditional vaccine group. Two-thirds of mRNA vaccine recipients reported symptoms such as fever, headache, fatigue, muscle pain, and diarrhea, while only about half of the traditional group did. Serious side effects were rare and occurred at similar rates in both groups, with no cases of myocarditis recorded.

Illustration of flu vaccine under research. Photo: Vecteezy

Experts believe that for widespread acceptance of mRNA vaccines, side effects need to be reduced. Many people, still recalling the fatigue after covid-19 vaccination, would hesitate to receive annual booster shots. Additionally, the study did not assess efficacy in individuals over 65, children, or those with chronic diseases, who are at the highest risk for influenza. Furthermore, the vaccine faces the challenge of potential budget cuts from the US government.

"Despite challenges, the mRNA flu vaccine is expected to help the world better cope with severe flu seasons and the risk of future pandemics", a representative for the research team stated.

According to the World Health Organization (WHO), as of 2/11, the predominant circulating flu strains are influenza A/H1N1, A/H3N2, and B. H3N2 is currently dominant in many regions. Influenza A can mutate quickly, easily causing major outbreaks. New evolutionary branches like H3N2 subclade K are being closely monitored as they could reduce vaccine effectiveness.

WHO and the US Centers for Disease Control and Prevention (CDC) continue to recommend annual flu vaccination. The vaccine still helps reduce the risk of hospitalization by 70-75% in children and 30-40% in adults, even when the virus mutates.

For many decades, seasonal flu vaccines have typically been produced by cultivating viruses in chicken eggs. This process takes about 6 months, requires a huge number of eggs, and is prone to viral mutation, which can reduce vaccine efficacy. Therefore, scientists are adopting new technologies to overcome these limitations. One promising direction is mRNA vaccine technology, which helped the world rapidly produce hundreds of millions of covid-19 vaccine doses during the pandemic.

Van Ha (According to Cidrap)