This fall, health officials are recommending individuals get an updated Covid-19 booster, as well as a seasonal flu vaccine. However, there is some debate about when people should get the vaccines to ensure that they are most protected.

Health officials recommend both Covid-19 boosters and flu shots for the fall

Earlier this month, federal officials authorized updated Covid-19 boosters from Pfizer-BioNTech and Moderna for a fall booster campaign in the United States. Pfizer-BioNTech's booster is authorized for individuals ages 12 and older, while Moderna's booster is authorized for all adults 18 and older.

The boosters are bivalent vaccines, which target both the original coronavirus variant and omicron subvariants BA.4 and BA.5. According to CDC guidelines, people are eligible for an updated booster dose at least two months after their last Covid-19 shot, whether it was a booster or an initial vaccine.

"As we head into fall and begin to spend more time indoors, we strongly encourage anyone who is eligible to consider receiving a booster dose with a bivalent Covid-19 vaccine to provide better protection against currently circulating variants," said FDA Commissioner Robert Califf.

At the same time, health officials are also recommending people get a flu vaccine ahead of a potentially severe flu season after countries in the Southern Hemisphere, including Australia and New Zealand, saw higher-than-average flu cases recently.

According to CDC, "September and October are generally good times to get vaccinated" against the flu. And while the agency said that "ideally" people should be vaccinated by the end of October, getting a flu shot later can still provide protection during the flu season.

Separately, health officials have suggested that annual Covid-19 boosters may be necessary, similar to annual flu shots, going forward.

"It is becoming increasingly clear that, looking forward with the Covid-19 pandemic, in the absence of a dramatically different variant, we likely are moving towards a path of vaccination cadence similar to that of the annual influenza vaccine, with annual updated Covid-19 shots matched to the currently circulating strains for most of the population," said Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases.

Should you get a Covid-19 booster and a flu shot at the same time?

As the United States begins its fall booster campaign, some health officials are urging people to consider getting their Covid-19 booster and flu shot at the same time. According to CDC, people can safely receive both vaccines at the same time, although they may be slightly more likely to experience side effects, such as fatigue, headache, and muscle ache.

To make it easier for people to get both vaccines at the same time, some local public health departments are planning joint vaccine clinics.

"Jurisdictions are going to be standing up joint flu and Covid vaccine clinics and other opportunities for people to get both their flu vaccine and their Covid updated booster together," said Lori Tremmel Freeman, CEO of the National Association of County and City Health Officials. She added that there is "no problem at all" with getting both shots at the same time or close together.

"I really believe this is why God gave us two arms—one for the flu shot and the other one for the covid shot," said Ashish Jha, White House coronavirus response coordinator.

However, some health experts say it may be too early to get a flu vaccine since protection typically decreases relatively quickly over the course of a flu season. For example, a study from researchers at the Kaiser Permanent Vaccine Study Center and the Harvard School of Public Health found that vaccine effectiveness declines by roughly 18% for every 28-day period.

"You've got about four months of pretty solid protection," said Emily Martin, an associate professor of epidemiology who specializes in flu at the University of Michigan School of Public Health.

If people get vaccinated against the flu right now, they may not be well protected if the flu season does not peak until February or March, much like it did in the 2021-2022 season. Instead, some health experts are recommending people wait until the end of October to get a flu shot unless flu activity begins to pick up earlier.

"I'll follow very carefully the activity in the community," said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy. "If it starts to pick up, I'll move immediately. Otherwise I'm counting on sometime in late October, early November."

On the other hand, other health experts argue that moving towards a joint administration approach with the Covid-19 and flu vaccines is the best way to simplify the vaccination process and increase overall coverage rates.

According to Ed Belongia, director of the Center for Clinical Epidemiology and Population Health at the Marshfield Clinic Research Institute in Wisconsin, public health authorities should consider what is best for the population as a whole, not just individuals, when planning vaccination campaigns.

"There's a tradeoff, right, between starting too early and having waning, versus missing opportunities to vaccinate," said Belongia. "In terms of trying to optimize timing, you lose people who don't get vaccinated at all. Trying to balance those is difficult because you don’t know when the flu season is going to begin each year."

Overall, pairing the Covid-19 and flu vaccines together will make it easier for people who want to get vaccinated and potentially encourage more people to get vaccinated overall—even if getting a flu vaccine earlier in the year may ultimately lead to lower protection.

Noel Brewer, a professor of health behavior at the University of North Carolina, said he thinks joint-administration is the right approach. "I don't think any of this is free. I don't think any of it's easy," said Brewer. "There isn't a single best option that we can do that doesn't have some consequences. We just have to take the less onerous consequence." (Branswell, STAT, 9/9; Howard, CNN, 9/12)