COVID-19 Booster Shots: What You Need to Know

Evidence-based research has shown that the COVID-19 vaccines currently in use in the US are remarkably safe and effective at preventing a severe reaction to the virus and keeping people out of the hospital. But their effectiveness has been found to decrease over time, leading the medical community to start recommending booster shots for eligible individuals. What could this mean for you?

Who should get a COVID-19 booster shot?

Broadly speaking, all Americans who are eligible should get a COVID-19 vaccine booster shot. Whether or not a booster is right for you is a decision you should make in consultation with your health care provider. Only they have your personal health information and the medical expertise to consider your whole health story.

A booster will be particularly important for individuals who are immunocompromised, as roughly half of the 7 million adults in that population have not shown a robust immune response to their initial vaccine. Thankfully, the booster has been found to provide an added level of protection for individuals who are immunocompromised—and every bit makes a difference.

Consider getting the COVID-19 booster shot if you: 

• Have had an organ or stem cell transplant and take immunosuppressant treatment to avoid rejection of the transplant
• Are in treatment for blood cancer
• Have an immune system deficiency due to a genetic disorder
• Are receiving dialysis
• Have a chronic medical condition such as kidney disease, or do not have a spleen
• Are receiving chemotherapy treatment, taking high dose corticosteroids, or using another medication that suppresses the immune system
• Have advanced or untreated HIV

When should you get the booster?

According to the Surgeon General, "We know that even highly effective vaccines become less effective over time."⁽¹⁾ Ongoing research is trying to nail down what that time period is for the COVID-19 vaccines currently in use, and it may vary by the brand and formulation of the vaccine you received (Pfizer, Moderna, or Johnson & Johnson).

So far, experts agree that a booster shot may be needed as soon as 6 months after the second dose of an initial vaccine (or in the case of single-dose Johnson & Johnson, after the first shot).

What factors impact vaccine effectiveness?

One, within a vaccinated individual, the initial surge of immune cells that cause the production of protective antibodies gradually drops off over time.

Two, viruses mutate (change) as they spread over time, particularly in unvaccinated populations where they spread rapidly. This explains the emergence and rapid spread of the much more contagious and virulent Delta variant of novel coronavirus. The Delta variant is extremely dangerous, causing high rates of illness and hospitalization among the unvaccinated. Delta also has also been shown to cause “breakthrough infections” among the fully vaccinated, emphasizing the need for a COVID-19 booster solution to combat the pandemic.

We reasonably expect new COVID-19 variants and the boosters made to fight them to generate much conversation and debate in America and around the world. As an expert from Emory University advised, "Discussions around boosters need to look at their incremental value to improving protection, from stopping transmission to preventing symptomatic infections and severe disease." ⁽¹⁾ 

How do vaccine boosters work?

Immunization is critical to public health, but to combat outbreaks, there needs to be sufficient immunity both at the individual and national population levels. In addition to getting the unvaccinated vaccinated, booster shots can help fill present gaps.

As with any vaccine, the initial immune response that stirs up antibodies (the proteins that fight a particular disease) will drop off slowly but leave behind protective cells to help the body fight future infection. A booster does several things for these protective cells. Mainly, it causes antibody-making cells to multiply, “boosting” your level of protection once more. In time, the cells will drop off again, but the pool of protective cells left behind will be larger than before, leading to a faster, stronger response to new COVID-19 exposures.

This means that a booster shot should produce a stronger immune response in an individual than their initial vaccine—giving you a better chance of staying healthy and out of the hospital.

When will people be eligible for a booster?

As health officials prepare to roll out booster shots in the US, all adults 65+ who received a two-dose vaccine will be eligible for a booster 6 months after the date of their second shot. The boosters will be widely available and free, and authorities are encouraging all vaccinated individuals to get the booster when it is their turn.

What is the future of COVID-19 boosters?

There is much more to learn not only about the COVID-19 vaccines, their long-term effectiveness, and the level of immunity they provide, but also the effect future variants may have on the health of American and global populations.

What we do know for sure is that COVID-19 vaccines and boosters are a critical solution to this pandemic—not only for our health, but for our return to a sense of normalcy as a society. We have come so far in only a short period of time, but much more needs to be done to combat this deadly virus, and boosters will likely be a big part of the puzzle to defeat COVID-19.

Clinically reviewed October 4, 2021

(1) Callaway, Ewen. "COVID vaccine boosters: the most important questions." nature.com. Aug 05, 2021. https://www.nature.com/articles/d41586-021-02158-6