Second COVID-19 Vaccine Booster Shots: Who Should Get One
An infectious diseases specialist explains what experts know about the safety and efficacy of a second booster shot.
In March, the Food and Drug Administration (FDA) authorized a second COVID-19 booster shot of the Pfizer-BioNTech and Moderna vaccines for people who received their first booster at least four months ago and fall into one of these categories:
- Age 50 and over
- Immunocompromised who are age 12 and over
- Received two doses of the Johnson & Johnson vaccine
Dr. Marcus R. Pereira, medical director of the Transplant Infectious Diseases Program at NewYork-Presbyterian/Columbia University Irving Medical Center and assistant clinical professor of medicine in the Division of Infectious Diseases at Columbia University Vagelos College of Physicians and Surgeons, shares why a second booster was recommended and what experts know about protection from prior infection.
What’s the rationale for authorizing a second booster?
I think multiple factors went into the decision. We know immunity starts to wane after four months or so, and the Omicron subvariant BA.2 appears more capable of breaking through our immunity. And then there’s the understanding that those over 65 and those who are immunocompromised were hardest hit by Delta and Omicron.
A recent Israeli study of a second booster also factored into the decision, even though it is not fully published yet. The study offered a second booster dose to people age 60 to 100 and then looked at mortality. After 15 days there was already a big difference in deaths and hospitalizations from COVID between the two groups. For those age 60 to 69, people with just one booster had a two-fold higher rate of death from COVID. And for those over 80, the rate was almost 10 times as high.
The FDA is taking into account BA.2 and what other variants may emerge next. The coming BA.2 wave could mimic what happened with Omicron, and older individuals and immunocompromised people will be hit hardest. In this case, a second booster is likely to provide added protection for these vulnerable groups.
Why limit the recommendation to people over 50?
A fourth booster does not seem to create much of a benefit when it comes to more severe outcomes for those who are younger.
This comes from another Israeli study, just published a few weeks ago in NEJM, that looked at the efficacy of a fourth dose of the vaccine in health care workers against Omicron. A second booster only provided a marginal benefit to those under 60.
The age 50 to 60 category, especially in those without health problems, right now is a gray zone. The data on efficacy of a second booster in this group is limited, so it’s hard to say what the benefit is. These individuals may do well with just one booster if they don’t have additional comorbidities. However, if cases are rising in their communities, then getting a second booster at this time may be of benefit.
Should I get a second booster now or wait?
Those in the age 50 to 60 category who are healthy and don’t have any additional comorbidities should talk to their doctors about when it would be reasonable to get the second booster, in particular in relation to rates of local transmission of the virus. This is because we now know that the effects of the vaccine wane after four to six months, so the timing is very important in order to maximize the benefits. It takes about a week for the effects of boosting to occur.
If you are immunocompromised or over age 60 or 65, I’d advise getting a second booster sooner rather than later, because the risks of COVID are still substantial.
Is a second booster dose safe?
These vaccines are very safe. Some transplant recipients have already received a fifth dose, and there hasn’t been any warning signal on multiple dosing. The recent NEJM study saw no safety issues.
If I’ve already been infected with Omicron, should I get a second booster?
The FDA authorization doesn’t mention this, but some experts suggest that an episode of COVID is potentially akin to a vaccine booster dose. If you’re otherwise healthy, you did well with Omicron, and you don’t foresee any risk factors coming your way—like you’re about to get chemotherapy or an organ transplant—it’s another situation in which you should talk to your doctor about whether it is reasonable to wait three to four months after COVID to get another booster.
The immunity benefit from getting Omicron will probably start to wane after four months. If there is a wave in the summer, like what happened last year with Delta, it is not clear that an Omicron infection from December or January would be a significant protective factor against a breakthrough infection, though it will probably offer good protection against severe disease, just as the first booster does after four to six months.
“If you are immunocompromised or over age 60 or 65, I’d advise getting a second booster sooner rather than later, because the risks of COVID are still substantial.”
— Dr. Marcus Pereira
Should I get my antibodies measured before getting a second booster?
I know in the transplant community, some physicians check antibodies against the spike protein as a way of giving clinical guidance. If antibodies look high, they may tell patients that it’s ok to take a bit more risk or travel.
But the problem is, we haven’t established definitive thresholds; we don’t have a number that tells us when your antibody level is protective. And with each variant, the threshold changes. We see that with the declining efficacy of the vaccine with each variant. It’s been very difficult to nail down a number.
I think a bad test is worse than no test. It will either give you a false sense of security or a false sense of panic, and I think that doesn’t help anyone make sensible decisions.
It’s safer to follow recommendations based on data from larger studies. So, if you fit into a category, like immunocompromised or over a certain age or comorbidities, then follow the guidance for now instead of trying to individualize your response.
If I got the Pfizer booster the first time, should I switch to Moderna and vice versa?
We’re seeing more “mix and match” studies, and when you look at data about the first boosters, there was a slight advantage of mixing the mRNA vaccines. These are different vaccines with slightly different mRNA sequences, and it makes sense that they would elicit slightly different immune responses.
Switching to a different vaccine for a second booster might not be a bad idea, but truth be told, there’s not a lot of evidence for it yet. We haven’t yet seen a mix and match study with second boosters, apart from some lab studies.
And we’re talking about diminishing returns with each additional dose, so any added benefit from switching vaccines may not be very significant.
The situation is different for those who got a J&J vaccine initially. Those people should get mRNA boosters.
What if I haven’t had a first booster yet? Is it too late?
People should go out and get a first booster if they haven’t had one yet. That’s because the evidence is strong that a booster dose prevents more severe outcomes with Omicron. It’s definitely needed and there is no controversy about this.
This piece was originally published on Columbia University Irving Medical Center’s Newsroom.
Marcus R. Pereira, M.D., MPH, is medical director of the Transplant Infectious Diseases Program at NewYork-Presbyterian/Columbia University Irving Medical Center and an assistant clinical professor of medicine in the Division of Infectious Diseases at Columbia University Vagelos College of Physicians and Surgeons. Dr. Pereira prevents and treats infectious complications in patients with solid organ and bone marrow transplants as well as hematological malignancies, and provides care in both inpatient and outpatient settings. In the Transplant Infectious Diseases Program, Dr. Pereira oversees the development of infection prophylaxis and treatment protocols for immunocompromised patients. His areas of interest include multi-drug-resistant infections, including bacterial and fungal organisms in transplant patients as well as resistant cytomegalovirus infections. He is an associate editor of the American Journal of Transplantation and has led several studies this past year on the impact of COVID-19 in solid organ transplant recipients.