Flu cases are picking up, and experts urge vaccinations now

As flu season is expected to intensify in the weeks ahead, public health experts are urging Americans to get vaccinated. Flu activity remains low overall, but it is rising in the western and southern United States, with many early infections linked to new mutations of last year’s H1N1 virus.

“Right now, there is no cause for concern, but this should be a good last call to get your influenza vaccination for this year because the vaccines work best if they’re taken before the influenza season starts,” Andrew Pekosz, co-director of the Johns Hopkins Center of Excellence in Influenza Research and Response, said during a news briefing.

CDC FluView data show flu cases rose 5.7%, with 4,811 people hospitalized for influenza in the latest reporting week — the highest mid-October total since the 2010-11 season. The CDC said seasonal flu activity is increasing in many parts of the country, though it still remains low.

The Mayo Clinic says H1N1 first began causing illness in humans during the 2009-10 flu season. In 2009, the virus was responsible for about 284,400 deaths worldwide.

Pekosz said this year’s influenza vaccine covers three different viruses.

“Usually there are different influenza viruses that cause infections at the beginning and at the end of flu season, so even if you hear about a potential mismatch with the H1N1 component, it’s really important to get the vaccine because the other two components look like they’re going to be pretty good matches for the viruses that are emerging early in the flu season,” he said.

This season’s flu vaccine is available in two forms: a traditional flu shot that contains live or inactivated viruses to trigger an immune response, and a first-of-its-kind mRNA vaccine from Moderna that instructs muscle and immune cells to produce protective antibodies.

Both vaccines take about two weeks to begin offering protection, according to the CDC.

The Food and Drug Administration approved Moderna’s mFLUSIVA for adults 50 and older in August. A Phase 3 clinical trial comparing the two types of flu shots found that mFLUSIVA reduced the risk of flu illness by about 27%, according to the FDA.

“The mRNA vaccine performed better in clinical trial than the standard influenza vaccine, but we still don’t know if that will translate to better protection this flu season,” Dr. Anna Durbin, director of the Johns Hopkins Center for Immunization Research, said during the briefing. “We look every year to see how good a match between the vaccine and the flu strains are, and I think we’re going to be looking at this particularly closely this season because we have a new vaccine.”

The FDA meets every spring to choose the strains that will go into the influenza vaccine. Durbin said that timing is early because traditional flu vaccines take a long time to produce. She added that an mRNA vaccine can be updated later, and the FDA is discussing that possibility.

Pekosz said the effectiveness of this year’s flu vaccines should become clearer once early data arrive from states such as California and Washington, where flu seasons begin sooner.

Flu symptoms typically begin suddenly and can include fever, muscle aches, cough, sore throat, headache, fatigue or gastrointestinal symptoms, according to Johns Hopkins Medicine. Symptoms usually last three to seven days.

Symptoms of a cold or COVID-19 can look similar, Pekosz said, and alongside flu and COVID vaccination he recommends that people keep home testing kits on hand to help identify what is causing their illness.

“It’s important to know what you’re infected with, particularly if you’re in a high-risk group for severe illness, because there are antivirals against influenza and against COVID-19 that have been shown to reduce symptoms as well as reduce the chances of you developing severe illness from either infection,” he said.

He noted that antiviral medications work best when started soon after symptoms appear.

This season’s COVID-19 and respiratory syncytial virus, or RSV, vaccines are well matched to the viruses now circulating, Pekosz said.

The CDC reported that COVID-19 infections are growing or likely growing in 10 states, including Utah and South Dakota, and declining or likely declining in 15 states, including California, Texas and Florida. In 24 other states, the rates are not changing, the agency said.

RSV rates are currently very low in most states and are close to normal seasonal levels, according to the CDC.