Over the past few weeks in my clinical practice I’ve had many conversations with patients about Covid boosters. Here’s some basic information to help make sense of it all.

What is Covid vaccine booster?

A Covid vaccine booster is simply an additional shot of the same vaccine. For example, if your first covid two shots were Pfizer, a booster is getting a third Pfizer shot. At this point, boosters are not a different strength or formulation of the vaccines.

Why are boosters being given?

For two reasons. 

First, some people with weakened immune systems might not have achieved a sufficient immune response to their first two Covid shots. Common examples of this situation are people on medicines to suppress their immune system to treat autoimmune diseases or to prevent rejection of an organ transplant. For such individuals, receiving a third shot will improve their immune system’s capacity to respond to Covid if they encounter it. 

The second reason for boosters is to restore immune protection from Covid that may wane over time. Thus far the biggest concern about waning protection is with the Pfizer vaccine. CDC data from September showed that beyond 120 days after the second dose of Pfizer, effectiveness of protection from hospitalization fell from 91 percent down to 77 percent. A study from Israel showed that among people 60 years or older who had been vaccinated 5 months earlier, those who had received a third shot of Pfizer were 19.5 times less likely to have severe Covid than those who had only received two shots.  

Protection from the Moderna vaccine seems to be waning less than Pfizer. The same CDC data that showed decreasing protection from Pfizer over time showed no such diminishment with Moderna. It found that Moderna vaccine continues be 92 percent effective against hospitalization even four months after the second shot.

Who should receive a booster?

There are two categories of people for whom the Centers for Disease Control (CDC) recommends a booster.

The first category are people with moderately or severely weakened immune systems. This includes people taking medicines that suppress their immune system to treat cancer or autoimmune conditions or to prevent rejection of a transplanted organ. It also includes people with conditions that impair the immune system such as certain cancers, immunodeficiencies, or advanced HIV. 

If you have a weakened immune system, you should receive a third shot of your Pfizer or Moderna vaccine at least 28 days after your second shot. The CDC did not make a recommendation about whether immunosuppressed people who received Johnson and Johnson should get an additional shot. But based on the recommendation of trustworthy experts, I recommend that immunosuppressed people who got the J&J get a booster with Pfizer, Moderna, or J&J.

The second category are certain individuals who received their second Pfizer shot over 6 months ago.

-If you are 65 years or older and received your second Pfizer shot over 6 months ago, you should get a Pfizer booster.

-If you are 18 years and older and have a health condition such as diabetes or heart disease, you are eligible to receive a third dose of Pfizer vaccine 6 months after your second one.

-If you are 18 years and older and live or work in a setting that puts you at risk of getting Covid, you are eligible to receive a third dose of Pfizer vaccine 6 months after your second one.  This category includes people who live in long-term care settings, along with teachers, grocery store workers, and health care workers. 

Should I get a booster if I received the Moderna vaccine? 

Only if your immune system is suppressed by a medicine or a health condition according to current CDC recommendations. But stay tuned because the FDA will be meeting on October 14 to discuss Moderna boosters and on October 15 to discuss J&J boosters.

Where should we get our Covid booster shot?

The simplest way is by making an appointment online with a pharmacy in your area. When you sign up for the booster, you can indicate you are in one of the categories that makes you eligible.

Can I get my flu shot and Covid booster at the same time?

Yes. The CDC states it is safe to do so.