When to get it and more

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

It is the third time since the first series that the vaccines have been updated to adapt to the strains in circulation. The shots should be available in the next few days. The agency has not yet approved a third vaccine from the pharmaceutical company Novavax.

The timing of the new vaccines' rollout – last year they were rolled out in mid-September – is significant because most of the U.S. is still in the grip of the summer wave of Covid cases. On Monday, the Centers for Disease Control and Prevention reported that the number of people testing positive for Covid continues to rise and that emergency room visits for Covid have increased since mid-May. Hospitalizations are also rising.

Here's what you need to know about the updated vaccines.

What is different about the new Covid vaccines?

The new vaccines from Pfizer and Moderna target the KP.2 strain, a descendant of the highly contagious JN.1 variant that was widespread in the U.S. last winter. The pharmaceutical companies began producing the new doses in June after the FDA advised them to adapt the formulations to the version of the virus that was surging in the U.S.

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

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

It is still unclear how effective the vaccines will be against the newer strains, but experts believe they will protect against severe disease.

A Pfizer spokesperson told NBC News that data submitted to the FDA shows that the company's vaccine produces a “substantially improved” immune response against several variants currently circulating, including KP.3, compared to previous versions of the vaccine.

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

A paper published this month in the journal Infectious Diseases notes that KP.3.1.1 shares similarities with JN.1 and KP.2, but has some additional mutations that may contribute to its easier spread.

“All of these changes are incremental. They don't change the bigger picture,” Moore said. “KP.3.1.1 is just another step in the journey that the entire Omicron line is taking toward greater portability.”

Who should receive the new Covid vaccine?

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

This means that every year we will receive an updated Covid vaccine to protect against mutations and waning immunity, just like with annual flu shots.

As of May 11, only 22.5% of adults had received last year's updated Covid vaccine, according to CDC data. Only 14.4% of children ages 6 months to 17 years have been vaccinated.

This fall, the CDC recommends the new vaccinations for all Americans ages 6 months and older.

But Dr. Isaac Bogoch, an infectious disease specialist at the University of Toronto, said it is difficult to make a blanket recommendation about who should receive the vaccine, especially for healthy, young adults.

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

It is critical that people at highest risk of severe Covid infection – including people over 65 or with weakened immune systems or underlying medical conditions such as heart disease or obesity – receive the vaccine, Bogoch said.

“The main role of the vaccine is to protect the most vulnerable people from serious consequences such as hospitalization and death,” he said.

When should I get the new Covid vaccine?

Millions of Americans have been infected with Covid in recent weeks and months. One benefit of the summer surge is that people who have recently recovered have strengthened immune systems to fight off future infections.

Because vaccines will be available earlier this year than last year, the question of when to get the best protection over the winter is more pressing. According to CDC guidelines, if you've recently had Covid, you should “consider delaying your vaccine dose for 3 months.”

Experts say people at high risk of severe disease should get vaccinated as soon as the vaccine is available, because infection may not provide as much protection as vaccination, says Dr. Ofer Levy, director of the Precision Vaccines Program at Boston Children's Hospital.

Protection against infection may vary depending on the severity of the infection, strain, and a person's age and health status.

For young and healthy people, getting vaccinated so soon after recovering from infection may not be as beneficial, said Akiko Iwasaki, a professor of immunology at Yale School of Medicine. High antibody levels from a recent infection could prevent the vaccine from stimulating new immune cells.

“If there are already many antibodies in circulation, these antibodies block the [vaccine] from doing their job,” she said. “That's one reason why it's not recommended to get vaccinated immediately after having 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 vaccinated now, but it may make more sense to wait because Covid cases tend to rise in 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.

Immediate vaccination is risk-free, but the initial vaccination protection may not last throughout the expected winter wave, said Sax.

“The good thing is that with our immunity from previous vaccinations or Covid disease or both, we are all not as at risk of getting seriously ill,” he said. “But if you really want to avoid infection completely, it is the post-vaccination antibody surge that occurs one to three weeks after vaccination that provides the greatest protection.”

Dr. Manisha Juthani, commissioner of the Connecticut Department of Public Health, said people who have recently had Covid can wait several months before receiving their current vaccine.

“Immunity wanes if you've had Covid or if you've been vaccinated,” Juthani said Wednesday during a press conference with the Association of State and Territorial Health Officials ahead of the winter respiratory virus season. “If you don't necessarily want to get vaccinated right away, wait about three months after you've had Covid, and especially so you get the vaccination before major holidays and before the time when you might be gathering with people.”

“If you feel strongly that you absolutely want to get the vaccine as soon as it's available, you can of course get it, even if you had Covid this summer,” she added. “There's nothing to stop you from being able to do that in September or October.”

Data from previous Covid vaccinations suggest that initial protection against infection peaks about a month after vaccination and wanes over the following months, even when the vaccine is well matched to the strains in circulation.

Fortunately, protection against severe disease lasts much longer, Iwasaki said.

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

“That's a pretty risky calculation because waves simply mean that there are a large number of infections in the population, but at the individual level you can still get infected tomorrow,” she said. “So it's very difficult to predict when the best time to get infected is.”

Iwasaki plans to get vaccinated herself sooner rather than later, as she has not been infected or received a booster shot in some time.

Sax recommends that his patients wait two to three months after recovery before getting vaccinated again.

“The reality is that your infection strengthens your own immunity,” he said.

What side effects do the new Covid vaccines have?

As with 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 fatigue,

How much will it cost?

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

The vast majority of people with public and private health insurance should not have to pay out of pocket for the updated Covid vaccines – as long as they stay with an in-network provider, said Jennifer Kates, director of the Global Health & HIV Policy Program.

Medicare and Medicaid require that vaccinations be free for patients. The Affordable Care Act, also known as Obamacare, requires private insurers to cover any vaccinations recommended by the CDC's Committee on Immunization and Director.

However, Kates added that the ACA requirement does not apply to grandfathered plans – that is, plans that existed before the ACA was passed – and short-term health insurance plans.

“People enrolled in these plans may have to pay a cost-sharing fee for the Covid vaccine or the vaccine may not be covered at all,” she said.

Children without insurance can receive free vaccinations through the government's Vaccines for Children program.

For adults without health insurance, the situation is a little different. The CDC's Bridge Access Program, which paid for vaccinations for uninsured adults, is expected to close in August due to lack of funding.

Once the funds are exhausted, uninsured people may be able to get free Covid vaccines through community health centers and other social security systems participating in the Section 317 adult vaccination program, Kates said. Section 317 is a federal initiative that provides funding to states to provide vaccines to uninsured or underinsured adults.

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