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Home » COVID-19 vaccine boosters FAQs – what you should know

COVID-19 vaccine boosters FAQs – what you should know

Following the advice of the Vaccine and Related Products Advisory Committee (VRBPAC), the FDA announced that COVID-19 vaccine boosters can be given to those individuals who received the Moderna and JNJ vaccines. This follows a previous announcement about the Pfizer vaccine booster shots. The FDA also stated that all eligible individuals could mix and match vaccines for their booster dose.

There is a lot of information about these boosters out there, so I thought I would take a moment to try to provide some facts and clarity about what the recommendations are about these COVID-19 vaccine boosters. Also, this is related to a US FDA set of decisions and recommendations from the CDC, so this article is going to only apply to the USA. However, don’t be surprised if the EU and other regulatory agencies across the world do the same thing.

COVID-19 vaccine boosters
Photo by Spencer Davis on Unsplash

Do COVID-19 boosters work?

A July 2021 study published in the peer-reviewed Nature Medicine estimated that COVID-19 vaccines with a 90% effectiveness dropped to 70% in about seven months and to 50% in about nine months. However, if you have a healthy immune system (and remember there’s no way to improve your immune system), these vaccines are very effective in preventing symptomatic COVID-19 infections, hospitalizations, and death.

The drop in effectiveness over time is probably a result of the new Delta variant but it also could be from a drop in antibody levels. A published study of the Pfizer vaccine found that protection against all variants and the Delta variant was 97% and 93% respectively one month after vaccination, but it declined to 67% and 53% four months later.

A preprint study also showed that the effectiveness of the Moderna waned over time.

Data presented to the FDA showed that COVID-19 vaccine boosters improved effectiveness immediately. However, we won’t know for a few months if those keep or lose effectiveness in the future.

person getting vaccinated
Photo by Gustavo Fring on

Get a booster if you are 18 or older with an underlying health condition

This should include people who are pregnant, obese, or immunocompromised, especially if you’re older than 50. Anyone with the following health conditions should get COVID-19 vaccine boosters:

  • Alcoholism
  • Cancer
  • Chronic kidney, liver, or lung diseases (such as moderate or severe asthma)
  • Dementia
  • Diabetes
  • Down syndrome
  • Genetic conditions, such as sickle cell disease or thalassemia
  • Cardiovascular diseases
  • HIV
  • Hypertension
  • Mental health conditions such as depression or schizophrenia
  • Smokers or former smokers
  • Stroke
  • Substance abuse
  • Tuberculosis
crop doctor writing prescription on paper
Photo by Laura James on

Get a booster if you are 18 or older and at risk due to your job.

Other individuals who work in certain occupations that are at high risk of COVID-19:

  • Healthcare workers
  • Firefighters
  • Police
  • Educators, such as teachers, daycare workers, and support staff
  • US postal workers
  • Public transit workers
  • Food and agriculture workers
  • Those who work in grocery stores, corrections, or manufacturing

Get a booster if you are 65 or older

Regardless of your job, lifestyle, or underlying health conditions (or lack thereof), get the COVID-19 vaccine boosters. The risk of hospitalization and death is much higher as you get older.

photo of hands touching baby bump
Photo by Jonathan Borba on

Get the booster if you’re pregnant

I have written previously about the importance of pregnant women getting the COVID-19 vaccine. Women who are pregnant, recently gave birth, or are considering getting pregnant should get the vaccine. The vast benefits far outweigh the rare adverse events. And pregnant women are eligible for COVID-19 vaccine boosters.

All adults who got the JNJ vaccine can get a booster

The FDA recommended that anyone who is 18 or older who received a J&J vaccine can get a booster two months after they received their dose.

The JNJ vaccine was originally approved as a single-dose regimen, even though it showed slightly less effectiveness at preventing hospitalization than the Moderna and Pfizer vaccines. However, it’s difficult, if not impossible, to compare results from different clinical trials, so a lot of vaccine experts thought that the results were probably similar between the vaccines.

However, some researchers thought that the JNJ vaccine should have been a two-dose regimen from the beginning, so the booster shot probably get its effectiveness up to a level comparable to the Pfizer and Moderna vaccines.

Go ahead, mix and match boosters

In the data presented to the VRBPAC, the researchers at the NIH found the following:

  • Moderna booster given to people who had previously received a J&J shot produced the most antibodies against the coronavirus. In fact, it showed a 76X increase in antibodies, an impressive number.
  • A Pfizer booster given to people who had received a J&J shot produced slightly fewer antibodies, about 30X more.
  • A J&J booster produced the least antibodies.

I think we should take the last point, using a JNJ booster for a JNJ original vaccine, as less credible. Apparently, the JNJ takes a bit longer to induce an immune response, and this study was done at 30 days. It’s possible that at 60 days all three booster regimens would show the same level of antibodies.

However, getting a Moderna booster after getting the JNJ vaccine may be the wisest choice.

calendar on mobile phone COVID-19 vaccine boosters
Photo by cottonbro on

When should you get the booster?

  • You should wait at least six months after the Moderna or Pfizer vaccine to get a booster
  • You should wait at least two months after the JNJ vaccine to get a booster.

COVID-19 vaccine boosters may be different doses

  • The Pfizer booster vaccine is a 30 µg dose just like the original vaccine doses
  • The Moderna booster vaccine is a 50 µg dose or half of the original 100 µg doses
  • The JNJ booster vaccine is the same as the first dose

Booster side effects

The rare adverse effects of the booster shots are probably going to be the same as observed with the original vaccinations. Most of the effects are mild, such as fever, headache, and nausea (all of which are signs that your immune system is being boosted by the vaccine). The more severe side effects, such as myocarditis, are very rare.

The effects of the COVID-19 vaccine boosters are not immediate

It takes time for the immune system to build antibodies that are needed to fight the SARS-CoV-2 virus. The booster does not provide instantaneous protection.

black wallet with dollar banknotes
Photo by Karolina Grabowska on

COVID vaccines boosters are free

If you are in the USA, the COVID-19 vaccines have been free for everyone. And it will be the same for the COVID-19 vaccine boosters.


Michael Simpson
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