FDA approves the new Covid vaccine. Here's the best time to get it. (2024)

The Food and Drug Administration on Thursday approved the new Covid vaccines from Pfizer and Moderna.

It’s the third time the vaccines have been updated to match circulating strains since the original series. The shots should be available within days. The agency hasn't yet approved a third vaccine, from drugmaker Novavax.

The timing of the new vaccines — last year's rollout was in mid-September — is significant, since most of the U.S. is still caught in the summer wave of Covid illness. As of Monday, the Centers for Disease Control and Prevention reported, the number of people testing positive for Covid keeps rising and emergency room visits for Covid have been increasing since mid-May. Hospitalizations are rising, too.

Here’s what to know about the updated vaccines.

How are the new Covid vaccines different?

The new shots from Pfizer and Moderna are designed to target the KP.2 strain, a descendant of the highly contagious JN.1 variant that began circulating widely in the U.S. last winter. The drugmakers started making the new doses in June after the FDA advised them to freshen the formulas to match the version of the virus that was gaining ground in the U.S.

A third vaccine, from drugmaker Novavax, has been updated to target the JN.1 strain. JN.1 and KP.2 have largely faded from circulation, according to the CDC.

As of Saturday, a sister strain called KP.3.1.1 accounted for about 36% of all new Covid cases, while another sister strain, KP.3, accounted for about 17%.

It’s unclear exactly how effective the vaccines will be against the newer strains, but experts expect that they will protect against severe illness.

A spokesperson from Pfizer told NBC News that data submitted to the FDA shows that its vaccine generates a “substantially improved” immune response against multiple currently circulating variants, including KP.3, compared to earlier versions of the vaccine.

There are “very minor sequence differences” between the variants, said John Moore, a professor of microbiology and immunology at Weill Cornell Medical College.

A paper published this month in the journal Infectious Diseases found that KP.3.1.1 shares similarities with JN.1 and KP.2, although it has a few additional mutations that may help it spread more easily.

“All these changes are incremental. They do not change the overall big picture,” Moore said. “KP.3.1.1 is just another step in the road that the overall omicron lineage is taking towards greater transmissibility.”

Who should get the new Covid vaccine?

In an earlier interview, Dr. Ashish Jha, dean of the Brown University School of Public Health and a former White House Covid-19 response coordinator, said Covid is most likely endemic in the U.S., meaning the virus is following “a relatively predictable pattern that will last a very long time.”

That means we’ll be getting a yearly updated Covid vaccine to protect against mutations and waning immunity, just like annual flu shots.

As of May 11, only 22.5% of adults got last year’s updated Covid vaccine, according to data from the CDC. Only 14.4% of children ages 6 months through 17 years got vaccinated.

For this fall, the CDC recommended that all Americans ages 6 months and older get the new shots.

But Dr. Isaac Bogoch, an infectious disease specialist at the University of Toronto, said it’s challenging to make a one-size-fits-all recommendation on who should get the vaccine, especially for healthy, young adults.

“It’s fair to say that the vaccines are still helpful, certainly at an individual level, and to some extent at a community level,” he said.

It’s critically important that people at the highest risk of a severe Covid infection — including people over 65 or with weakened immune systems or underlying health conditions, such as heart disease or obesity — get the vaccine, Bogoch said

“The heavy lifting of the vaccine is really in protecting the most vulnerable people from severe outcomes, like hospitalization and death,” he said.

When should I get the new Covid vaccine?

Millions of people in the U.S. have had Covid within the last few weeks and months. An advantage of the summer wave is that people who have recently recovered have an immune boost to fight off future infections.

Because the vaccines will be available earlier this year than last, the question of timing for the most protection through the winter is more urgent. According to CDC guidance, if you’ve recently had Covid, “you may consider delaying your vaccine dose by 3 months.”

For people at high risk of severe illness, experts say get the vaccine when it becomes available. That's because infection may not provide as much protection as vaccination, said Dr. Ofer Levy, the director of the Precision Vaccines Program at Boston Children’s Hospital.

Protection from infection can vary based on the severity of infection, the strain, as well as a person’s age and health.

For the young and healthy, it may not be as beneficial to get the vaccine so close to recovery from infection, said Akiko Iwasaki, professor of immunology at the Yale School of Medicine. High levels of antibodies present from recent infection may prevent the vaccine from stimulating new immune cells.

“If there’s a lot of antibodies already circulating, those antibodies are going to block the [vaccine] from doing its job,” she said. “That’s one reason why it’s not recommended to get the vaccine immediately after you’ve had Covid.”

Dr. Paul Sax, clinical director of the division of infectious diseases at Brigham and Women’s Hospital in Boston, said there’s no harm in getting the vaccine now, although it may make more sense to wait since Covid cases tend to pick up around November.

“Assuming that’s the case again this year, I would say sometime in October when people get their flu shot would be perfect,” Sax said.

There’s not a risk to getting it right away, but the initial protection from the vaccine may not last through an expected winter wave, Sax said.

“The good thing is that all of us with our immunity from prior vaccines or getting Covid or both don’t have as much of a risk of severe disease,” he said. “But if you want to really completely avoid getting infected it’s that antibody spike after the vaccine that happens one to three weeks after that’s most protective.”

Dr. Manisha Juthani, commissioner of the Connecticut Department of Public Health, said that people who recently had Covid can wait a few months before they get their updated vaccine.

“Immunity does wane from having had Covid or getting the vaccine,” Juthani said Wednesday during a media briefing with the Association of State and Territorial Health Officials ahead of the winter respiratory virus season. “If you don’t feel strongly about getting the vaccine right away, then waiting about three months from when you had Covid, and particularly, so that as we’re approaching the holidays, that you get that shot before the big holidays and when you may be gathering with people.”

“If you feel strongly that you really want to get the shot as soon as it’s available, even if you had Covid this summer, then of course you can get that,” she added. “There’s nothing to say that you can’t in September or October.”

Data from prior Covid vaccines suggests that the initial protection against infection peaks about a month after the shot and starts to wane over the next several months, even when the vaccine is well matched to the circulating strains.

Fortunately protection against severe disease remains robust for much longer, Iwasaki said.

Ultimately you never know when you may become infected with the virus, she said.

“It’s kind of a risky calculation because waves just means that there is a large number of infections in the population, but at the individual level you can get infected tomorrow,” she said. “So it’s very difficult to predict what is the best time to get it.”

Iwasaki plans to get the vaccine herself sooner rather than later since she has not been infected or had a booster in some time.

Sax recommends that his patients wait two to three months after recovering before getting another shot.

“The reality is, your infection gives you some boost of your own immunity,” he said.

What are side effects of the new Covid vaccines?

Like other versions of the Covid vaccines and similar to flu shots, the most common reaction is some pain at the injection site. Other side effects include:

• Tiredness
• Headache
• Muscle pain
• Chills
• Fever
• Nausea

The CDC says the side effects typically resolve after a few days. Serious side effects, such as the life-threatening allergic reaction called anaphylaxis, are rare.

Pfizer and Moderna’s vaccines have been associated with a small but increased risk of myocarditis, the inflammation of the heart muscle, mostly in young men. Most people make a full recovery.

How much will it cost?

Pfizer, Moderna and Novavax are charging up to $150 per dose for a Covid vaccine, according to data from the Centers for Medicare and Medicaid Services.

The vast majority of people with public and private health insurance should pay nothing out of pocket for the updated Covid vaccines —as long as they stick with an in-network provider, said Jennifer Kates, director of the Global Health & HIV Policy Program.

Medicare and Medicaid require that the vaccines are free for patients. The Affordable Care Act, also known as Obamacare, requires private insurers to cover all vaccines that are recommended by the CDC’s vaccine committee and director.

However, Kates added that the ACA’s requirement does not apply to grandfathered plans — plans that existed before the ACA was signed into law — and short-term health plans.

“People enrolled in these plans may face cost sharing for the Covid vaccine, or the vaccine may not be covered at all,” she said.

Children without insurance can get free vaccines through the government-run Vaccines for Children Program.

For adults without health insurance, the situation is a bit different. The CDC’s Bridge Access Program — which has been paying for shots for uninsured adults — is expected to shut down in August because of a lack of funding.

Once the funding runs out, uninsured individuals may be able to access free Covid vaccines through community health centers and other safety net providers that participate in the Section 317 vaccine program for adults, Kates said. Section 317 is a federal initiative that gives funding to states to provide vaccines for uninsured and underinsured adults.

“Some state and local health departments may also have a limited supply for people without insurance, but any supply will be very limited,” Kates said.