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The updated vaccines have not been specifically tested for safety in people, just as flu vaccines are not tested in people every year with a strain change. The safety of the shots, however, has been well established in the original trials and through surveillance of billions of highly similar doses.

The main serious safety risk of each of the vaccines is inflammation of the heart muscle or its surrounding tissue, known as myocarditis and pericarditis, respectively. The conditions are rare, most commonly affecting young men after a second dose.

Studies have shown that for most people, myocarditis is much more likely following a COVID-19 infection than a COVID-19 vaccine. Infection-related myocarditis is also more severe and linked to worse outcomes.

U.K. health officials analyzed preliminary flu data and predicted that subclade K may spread more easily than other versions. The researchers estimated that the reproduction number of subclade K is 1.4, meaning that each infected person spreads the virus to 1.4 other people on average. Typically, the reproduction number of the flu is closer to 1.2.

While there will be more flu cases this year, so far, there is no evidence that this new flu version will cause more severe cases, hospitalizations or deaths. Health officials have already recorded many more cases this year than at the same time last year, about 4.5 million cases compared to 1.9 million in 2024. But of those nearly two million cases last year, 1.2% were hospitalized and 0.05% died from their infections. So far in 2025, the rate of hospitalization is 1.09% and the mortality rate is 0.04%.

The CDC has not yet commented on the effectiveness of this year’s flu vaccine in the U.S. But U.K. health officials previously estimated that their vaccine, which is different from the one used in the U.S., reduced hospitalizations by about 70-75% in kids and by about 30-40% in adults.

The recent firing of the director of the U.S. Centers for Disease Control and Prevention (CDC) and new restrictions from leaders at the U.S. Food and Drug Administration (FDA) about who will be eligible to get COVID-19 vaccines have sparked confusion among the public and concern from health experts, who say it’s critical to protect as many people as possible from respiratory viruses like flu and COVID-19.

To answer some of your top questions about the 2025-2026 COVID-19 and flu vaccines, we consulted with infectious disease expert, Dr. Michelle Barron.

You can get both shots at the same time, and the exact timing doesn’t matter. So if you’re able to get the updated 2025-2026 COVID-19 and flu vaccines sometime in the next couple of months, Barron encourages as many people as possible to do so.

The panel originally had been scheduled to vote on the COVID-19 vaccine recommendations in June. But that month, Health and Human Services Secretary Robert F. Kennedy Jr. dismissed the committee and installed new members of his choice. The CDC director, who had just been confirmed by the Senate, was fired in August, and other top officials resigned. Meanwhile, Kennedy has repeatedly made false or misleading claims about COVID-19 vaccines this year.

This year, the recommendation by the Centers for Disease Control and Prevention is narrower. Although the vaccines are broadly recommended for adults 19 and older, they are no longer recommended for healthy pregnant people or for healthy children 6 months through 17 years old.

Kennedy announced the changes in a video in May, citing safety risks for young people and pregnant people as justification.

But his claims have been widely disputed by experts in vaccines, pediatrics, and women’s health. An analysis by FactCheck.org found that the secretary “misrepresented scientific research to make unfounded claims about vaccine safety for pregnant people and children.”

The measles, mumps and rubella vaccine is safe and provides 97% protection against the disease after two doses. Most children in the U.S. are required to get the shot to attend school. But vaccination rates have declined as more parents waive the shots or have fallen behind on recommended vaccination schedules.