What you need to know about the second booster

Last week, the Food and Drug Administration and the Centers for Disease Control and Prevention authorized a fourth dose of the COVID-19 vaccine for people 50 years and older, as well as some immunocompromised people.

The decision was made at a time when COVID-19 cases and hospitalizations in the United States have been declining. At the moment, more than 99% of U.S. counties have low or medium COVID-19 community levels, according to CDC data.

So why would someone need another booster at a time where the virus is circulating at relatively low levels? Yahoo News spoke to Katelyn Jetelina, an epidemiologist at the University of Texas Health Science Center, to break down what Americans need to know about the second booster.

Why is another booster needed?

There are two main reasons that U.S. federal health agencies recommend another booster for some higher-risk individuals. One reason is that there’s some evidence that vaccine protection against infection and serious outcomes from COVID-19 wanes over time, particularly for those who are older and immunocompromised.

One study conducted by the CDC found that vaccine effectiveness against Omicron, a COVID variant that is more transmissible and can evade vaccine immunity, was decreasing over time. According to the study, vaccine effectiveness against emergency and urgent care visits was 87% two months after a third dose, but it decreased to 66% by the fourth month after a third dose. Vaccine effectiveness against hospitalizations was also slightly decreasing, although the study showed it largely held up five months after the third dose.

Another reason a second booster is recommended at this time is that the United States is bracing for a new COVID-19 wave driven by a more transmissible Omicron subvariant known as BA.2. The strain, which has been driving new COVID-19 surges in China, the United Kingdom and Europe, has recently become dominant in the U.S., according to CDC data. BA.2 now accounts for about 72% of new coronavirus cases nationwide, according to the agency.

There are early signs that the BA.2 infection wave has already begun. Over the past two weeks more than a dozen states, the majority in the Northeast, have seen an uptick in cases. In New York, Massachusetts and New Jersey, cases are up by more than 30 percent, according to New York Times data.

Although the ultimate impact of BA.2 in the U.S. is yet to be seen, health experts don’t foresee the variant causing a major surge as it did in Europe. However, Jetelina says deploying an additional booster now is a “proactive move” to stay one step ahead of the virus, which “is mutating pretty quickly.”

“Too many people have waning antibodies, and there's still a benefit to protecting against that new wave that may or may not come,” she said.

What are the benefits and risks of a fourth dose?

Most of the data that drove the FDA’s and CDC’s decisions to authorize a second booster comes from Israel, where the additional dose was rolled out a few months ago, Jetelina said.

“There's really two debates that are going on right now with the booster: Are our vaccines meant to protect against infection or are they meant to protect against severe disease and hospitalization? And what we’re seeing with the fourth dose is that there's benefit to both of those in Israel [for older adults],” she said.

There are currently three studies of the second booster from Israel that support this. One of the studies looked at approximately a million people ages 60 and older who had received a fourth dose at least four months after the third dose.

According to this study, “a fourth dose reduced the rate of infection by two times and reduced the rate of severe disease by four times, making it four times lower,” Jetelina said. “So again, a second booster or a fourth dose has a meaningful impact on older adults.”

Another study, and perhaps the most important of the three, was conducted at Clalit Health, one of Israel’s largest health care organizations, among people over 60 and also four months out from their third shot. This one showed Israelis who received a second booster reduced their chances of death by 78%.

But what about the younger population? Jetelina says there are not many studies yet looking at the effectiveness of a fourth dose among young people. But one small study, also conducted in Israel among health care workers, found that a fourth dose increased antibodies, which would reduce the chances of infection.

“But beyond that, immunity looked to kind of max out with healthy adults,” Jetelina said. “In other words, there's really no meaningful increase in the quality of the immune system after a four dose among the young population, and so there was a little added benefit of efficacy but not statistically significant,” she added.

Based on this study, and the lack of evidence available at the moment to support a second booster for those who are younger and healthy, Jetelina thinks it is unlikely that the additional dose will be recommended for people under 50 in the United States. However, that may change, she says, if other variants of concern emerge and as the fall season approaches. This is a time where COVID-19 cases are expected to go up and when people’s vaccine immunity may start to wane.

In terms of safety, the FDA said last week that “the known and potential benefits of a second COVID-19 vaccine booster dose with either of these vaccines outweigh their known and potential risks” in the populations who are now eligible for the shot.

Who is eligible for a second booster?

Based on the FDA and CDC recommendation, a second booster of the Pfizer-BioNTech or Moderna vaccines may now be administered to certain immunocompromised individuals and people 50 and older at least 4 months after they received a first booster dose of any authorized or approved COVID-19 vaccine.

People 12 and older with certain kinds of autoimmune disorders, such as those who have undergone organ transplants, will also be eligible for a second booster dose of the Pfizer shot, the FDA said, while those 18 and older who are qualified to receive a shot can choose between Pfizer’s and Moderna’s.

The CDC is also recommending that adults who received the one-dose Johnson & Johnson primary series and received a booster at least four months ago get a second booster using one of the two mRNA COVID-19 vaccines available — Moderna or Pfizer.

Many people are asking why both the FDA and the CDC are recommending the additional dose for people ages 50 years and older when most of the research in Israel that drove the decision studied individuals who are 60 and older. On Monday, Peter Marks, who oversees the FDA’s vaccine division, explained why.

“The reason why we felt it was very reasonable to include the 50 to 65 age range is because about a third of people in the United States in that age range have medical comorbidities,” Marks said on “In the Bubble with Andy Slavitt” podcast. “The safety is excellent and the idea here is that, you know, it is sometimes easier to just say, ‘Look, we know in general with respiratory viruses people over 50 years of age tend to have more problems than people under 50 years of age. Maybe it’s a good idea just to boost everyone here in the event we have another wave,’” he added.

Should you get a second booster now or wait?

Many experts, including Jetelina, have said the second booster can certainly wait if you’re healthy and the virus circulation where you live is very low. But if you live or work somewhere where cases are high or are rising, or if you are traveling or have other plans that would put you at increased risk, it makes sense to go ahead and get the fourth dose now.

For those who plan to wait, Jetelina cautions against trying to time a booster right before a wave. “We know that this virus continues to mutate and a variant of concern could pop up. We also know that boosters take time to work to their full potential,” she wrote in a newsletter she authors called “Your Local Epidemiologist.” “Finding a timing sweet spot of boosting before a wave is possible, but potentially risky with not much added benefit,” she added.

Dr. Monica Gandhi, an infectious disease expert and professor of medicine at the University of California, San Francisco, told CNET that a good strategy might be to plan your second booster before the fall, which is when COVID cases and other respiratory viruses tend to go up.

"I'd rather my parents get the booster in late summer, so they're fully protected in the fall," Gandhi said.

If you have received your first booster and have had a confirmed case of Omicron infection, Jetelina and other experts have said you can certainly wait.

“There’s actually really no need or very little need to get a fourth dose, and that’s because of this thing called hybrid immunity,” Jetelina said. “Many studies have shown that this actually is very fantastic protection and that’s because the vaccine immunity is directly toward the spike protein, whereas infection-induced immunity is directed toward the virus as a whole,” she explained.

Both the CDC and the FDA recommend a fourth dose regardless of previous infections. However, Jetelina said hybrid immunity is a viable path to protection that she hopes both agencies will soon recognize.

What most experts recommend getting immediately, if you haven’t yet, is the first booster, which is essential for maintaining a high level of protection against severe disease from all the Omicron strains.

“A third dose is incredibly important against Omicron and that’s because there’s really some serious immune invasion with Omicron, as well as waning protection over time. … People need to get that booster as soon as possible for ultimate protection,” Jetelina said.

Where can I get my second booster?

Last week, the Biden administration announced it was launching COVID.gov, a new one-stop-shop website where individuals can find out where to access vaccines, tests, treatments, and high-quality masks.

To find a booster near you, you can visit the site now. You can also find booster information at vaccines.gov.