Vaccines against the flu and COVID-19: What you need to know

Autumn's arrival heralds cool temperatures, warm sweaters, and anticipation of the upcoming holiday season. But it's also when infectious respiratory viruses start to spread more readily. That's why October is the ideal time to shore up your immunity against two common, potentially life-threatening viruses: influenza (flu) and SARS CoV2, the virus that causes COVID-19.

Winter warning: A bad flu season ahead?

With all the attention on COVID over the past two years, the focus on flu has waned somewhat. Last year's flu season was very mild — in fact, the peak number of positive cases was the lowest in at least the 25 years prior to the COVID-19 pandemic. But don't count on a repeat this winter.

"The general consensus is that this year's flu season could be worse than average, for a couple of reasons," says infectious disease specialist Dr. John J. Ross, assistant professor of medicine at Harvard Medical School.

First, Australia had a particularly severe flu season this year, with three times the normal amount of cases. Australia is in the southern hemisphere and their winter flu season peaks in August, often predicting what happens in the United States and elsewhere in the northern hemisphere, he notes. Second, the masking and social distancing that many people followed to prevent COVID also prevented the flu. "But the era of widespread masking has ended, so we're expecting more viral transmission this season," says Dr. Ross.

Continued complications from COVID-19

COVID cases and hospitalizations have dropped dramatically since earlier this year. On average, about 340 people died each day from the virus in August and September, compared to about 3,400 per day in early February 2022. "We expect that COVID rates will rise again over the winter, although not at the same magnitude as last winter," Dr. Ross says. There's clear evidence that Omicron — currently the most widely circulating COVID variant — spreads more easily than earlier strains, but it's less likely to kill you, he adds.

Flu vaccine advice for adults

All adults should get an annual flu vaccine, with the rare exception of people who've had a life-threatening reaction to the shot in the past. The vaccine is especially important for those with a higher risk for serious complications from the flu. This includes

• people over age 65
• residents of nursing homes and other long-term care facilities
• people who have heart failure and other cardiac conditions, or who suffer from asthma, COPD, or other lung diseases
• people who have Parkinson's disease, multiple sclerosis, strokes, or other neurological problems
• people who have diabetes, weak immune systems, and chronic liver or kidney disease
• pregnant women and new mothers.

If you're over 65, the CDC recommends getting one of the vaccines that produces higher levels of antibodies that help protect you against the flu: the Fluzone High-Dose Quadrivalent, Flublock Quadrivalent recombinant, or the Fluad Quadrivalent adjuvanted vaccines. The first two contain higher amounts of antigens, the proteins that trigger the body's antibody response. The third contains an adjuvant, which is an additive that enhances immune response. People who fall into the other high-risk categories mentioned above might also want to seek out one of these vaccines, says Dr. Ross. But get the standard flu vaccine if none of the other options are readily available.

COVID vaccine advice for adults

The CDC is urging all adults to also stay up to date with COVID vaccines, including the new bivalent mRNA booster. The bivalent shots target both the original COVID strain and the two most recent Omicron subvariants (BA.4 and BA.5), which are more contagious than earlier strains. You should wait at least two months after your previous booster or primary vaccine series to get the new booster. Booster recommendations may differ for people who have a weakened immune system. See the CDC website for more detail on COVID vaccines and boosters.

"The real-world effectiveness of these boosters is a big question mark, but I certainly recommend one to anyone who's due for a booster, especially if you're older," says Dr. Ross. Certain data from the earlier rounds of boosters suggests that anything you can do to expand your immune system's repertoire of response to Omicron will likely protect you against severe disease and hospitalization from COVID, he adds. For example, a recent study among nursing home residents shows 26% fewer COVID infections, a 60% reduction in hospitalizations, and a 90% reduction in deaths for those who had received two booster shots at appropriate intervals compared with only one booster shot.

There's no downside to getting the booster at the same time you get your annual flu shot, although those who experienced unpleasant side effects from a COVID vaccine in the past might want to get their flu shot on a different day. But for many people, getting both shots over and done with is a smart strategy.

What else can I do to avoid viral infections?

Simple measures such as washing your hands often, using hand sanitizer when you can't wash your hands, and avoiding touching your eyes, nose, and mouth can help you stay healthy. Also, be sure to eat well, stay active, and get a good night's sleep.

The CDC has additional advice for protecting yourself against COVID-19, such as moving indoor activities outdoors, improving ventilation of indoor air, and taking precautions like wearing masks and distancing when in crowded places, or when COVID cases are high in your community.