Influenza vaccines do not prevent milder cases

Influenza vaccines are not preventing this season’s dominant variant of the virus from causing mild or moderate illness requiring medical treatment, according to an interim analysis by US government-led researchers.

The efficacy of the formulation in preventing such cases was estimated at 16%, which was statistically indistinguishable from not being vaccinated, according to the study led by the Centers for Disease Control and Prevention (CDC). from the United States. The findings were reported Thursday in the agency’s Morbidity and Mortality Weekly Report.

Vaccination is still recommended for people older than 6 months while the virus is circulating, the CDC said. The vaccines can still prevent severe cases, hospitalizations, intensive care admissions and death, and may work against other variants that emerge later in the season, the authors said.

Health officials have long advocated for vaccines to protect against the viral winter illness that typically kills about 36,000 Americans a year, most of them elderly or in poor health. However, influenza constantly mutates and the vaccine, which is reformulated every year, never provides perfect protection, leading some people to doubt its overall benefits.

The widespread focus on the pandemic and public concerns about vaccines to prevent COVID may also have had an impact on vaccination rates. Doses distributed this season beginning in the third week of February fell 10% from a year ago, according to the CDC website.

The analysis was based on six months of data from more than 3,600 people with acute respiratory illnesses in California, Michigan, Pennsylvania, Tennessee, Texas, Washington and Wisconsin. The low number of cases prevented researchers from estimating efficacy in different age groups, according to the study.

Estimates of vaccine efficacy could still change at the end of the season as more people become infected or if other variants of the virus predominate later in the season, the authors said. Influenza cases in the United States typically peak between December and February, but can last into May.

“Influenza activity is difficult to predict, and strategies to prevent illness remain important to reduce pressure on health care services,” the authors concluded.

The CDC has also suggested the use of antiviral drugs, including Tamiflu, in addition to vaccination. Such drugs may also offer protection against variants of influenza that could circulate later in the year.

With the success of messenger RNA vaccines against COVID-19, vaccine makers Moderna Inc. and the Pfizer Inc.-BioNTech SE partnership are exploring the possibility of using the same approach for influenza vaccines. While the researchers anticipate that the technology will one day allow scientists to improve the efficacy of existing vaccines, it can be a long and complicated task.