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Common Questions About COVID Vaccine Boosters

"Should I get it or not?"

Key points

  • A COVID-19 "booster shot" is an additional dose of the vaccine that is intended to bolster immunity.
  • Health organizations and scientists disagree about whether booster shots are necessary at this point in the pandemic.
  • Currently, only certain people in certain countries are eligible for booster shots.

While the fight against COVID-19 has been reinforced with vaccines and mass immunization, new variants continue to spread across the globe. One possible way to tackle new variants is with COVID-19 vaccine booster shots, a measure currently being investigated and/or pursued by governments in the U.S. and other countries. The main focus of this post is to shed light on the COVID-19 vaccine booster, its purpose, and whether it’s really necessary.

What is a booster shot?

A COVID-19 vaccine "booster" is a vaccine containing the same dose as administered in the two-shot regimen. The primary objective of giving booster shots is to mobilize defenses of the immune system for better protection against COVID-19 and its variants. In other words, booster shots are intended to make people more resilient to COVID-19, especially if we bear in mind that vaccines such as Pfizer have been shown to protect against Delta and other variants, but their effectiveness decreases over time.

Are booster shots necessary?

Booster shots have become a subject of many debates, and it's highly likely there won't be a definitive answer to this question for a while. Recent evidence, issued by a large Israeli healthcare provider, shows that a third dose of Pfizer BioNTech vaccine was 86 percent effective in subjects older than 60. The health authority, HMO Maccabi, compared results from 149,144 people older than 60 who received the third dose of the COVID-19 vaccine at least a week ago before the survey. These data were compared to those of 675,630 people who received only two doses of vaccine in January and February 2021.

Results showed that 1,064 people from the second group got infected with COVID-19. On the other hand, there were only 37 positive cases among persons who had a booster shot. Information about the severity of symptoms in 37 people who got COVID-19 after the booster vaccine was not provided.

Pfizer has stated that the effectiveness of their vaccine decreases with time. For that reason, booster shots—i.e., a third dose—demonstrated significantly more neutralizing antibodies against the initial virus (SARS-CoV-2) as well as Delta and Beta variants, which are highly infectious.

In July 2021, Israel started administering the third dose of Pfizer vaccine as a response to the increasing cases of COVID-19 induced by the Delta variant. The third dose was administered to 1.1 million eligible citizens of Israel, which includes healthcare workers, among others.

Besides Israel, many European countries and the United States are expected to offer booster shots.

Following the encouraging news from Israel, Pfizer and BioNTech submitted an application seeking authorization of a third or booster dose of their vaccine. As an argument for approval of booster shots, Pfizer confirmed the effectiveness of their vaccine wanes over time. They reported an effectiveness of 84 percent from a peak of 96 percent four months after receiving the last (second) dose of the vaccine.

Additionally, Pfizer and BioNTech reported subjects in their trial received vaccines eight to nine months after they had received the second dose. The drugmakers are expected to submit the same application to other healthcare regulatory bodies such as European Medicines Agency.

When it comes to booster shots, it is important to note that the FDA issued a statement on August 12, 2021, confirming that they approved the third dose of Pfizer and Moderna vaccines for immunocompromised persons. More precisely, the third dose of the COVID-19 vaccine can be administered to persons who are solid organ transplant recipients or diagnosed with conditions that compromise the immune system defenses.

Not everyone agrees with booster shots.

As many nations prepare to administer COVID-19 vaccine boosters, some organizations and scientists do not agree with this move.

On August 10, 2021, the World Health Organization issued a statement on vaccine boosters. In the statement, WHO recognizes several reasons why boosters might be necessary. These include:

  • Waning protection against COVID-19 over time, especially from serious disease symptoms
  • Decreased protection against variants of concern
  • Insufficient protection from the currently recommended primary series for some risk groups

However, in the conclusion of the statement, WHO stated that in the context of global vaccine supply constraints, booster doses may exacerbate inequities caused by increased demand and limited supply. In other words, WHO believes booster shots would only amplify the difference between countries—as those with higher incomes would be able to administer them, but nations with lower incomes are struggling to administer even the standard vaccine doses. The main focus, they argue, should be on administering the primary series of vaccines.

The WHO statement also argued that vaccine boosters should be introduced with strong evidence, yet current evidence is inconclusive and limited. While WHO is not entirely against vaccine boosters, the statement said, the organization is not up for it at the moment.

Some scientists have also criticized the American government’s decision regarding vaccine boosters. They argue that the data they use isn't compelling, and while it suggests there is a reduction in protection from mild to moderate cases of COVID-19, the standard two doses can still help protect from severe symptoms and hospitalizations.

Data suggest that COVID-19 vaccines are still effective in protecting vaccinated persons from hospitalizations and severe symptoms. Researchers explain vaccine boosters should be considered only in instances when the number of hospitalizations among vaccinated people increases significantly.

The human immune system is complex. Even though the presence of antibodies created by the vaccine may decline with time, the body also has other mechanisms that may protect an individual from severe disease. One of these mechanisms is T cells.

Where will booster shots be offered?

New variants of COVID-19 keep spreading worldwide, especially the Delta variant. A drastic increase in COVID-19 cases has already occurred in some countries and may worsen even still in fall and winter.

One possible way, then, to fight the surge in COVID-19 infections and protected high-risk groups in many countries is to offer booster vaccines. Israel has already administered over one million third doses of Pfizer to persons older than 50 and received their first two doses over five months prior. Recipients who received a third dose are 2.5 times more protected from infection compared to their counterparts who received two doses of Pfizer’s COVID-19 vaccine. This extra protection reaches its peak a week after administration of the third dose.

Turkey also went forward with the administration of the third dose in July 2021. Thailand and Cambodia are offering third-dose AstraZeneca to people who have received Sinopharm and Sinovac vaccines. Ecuador is planning to offer AstraZeneca, Pfizer, and Sinovac booster vaccines to persons with weakened immune system defenses. And the United States is now offering the booster to similar patient populations. (The FDA has granted full approval to the Pfizer BioNTech vaccine in recent days.)

The administration of third doses of COVID-19 vaccines to the elderly and vulnerable persons is also expected to take place in France and Germany in September. Plans are also to start with booster doses in the UK.

Who will be able to receive the COVID-19 vaccine booster?

The booster program in the U.S. is set in place, but the third dose of the COVID-19 vaccine is not necessary for everyone. The priority will be to strengthen the immune system of healthcare providers and older adults, including those in long-term care facilities.

Keep in mind the third dose was already approved for persons with a compromised immune system. It is useful to mention that health officials from the Biden administration recommended booster shot for Americans older than 18 and who are fully vaccinated with Moderna or Pfizer vaccines. However, the priority could be to vaccinate high-risk groups first. Remember, the FDA needs to approve the booster plan first and the U.S. is hoping to officially start on September 20 of this year.

How long to wait after vaccination to get a booster shot?

The booster plan still needs approval, and that is when all details will be clear. At this point, it is necessary to wait at least eight months after the first two doses to get a vaccine booster. So if a person was fully vaccinated in July, they wouldn’t be able to get a booster shot in September. Currently, the recommendations note that the booster should be the same shot that was given for the original vaccine—so if you had Moderna, you would need to get that booster shot.


The global fight against COVID-19 is still ongoing, but unlike in the beginning, the world has vaccines that strengthen immune defenses. As new variants keep spreading, booster shots are being considered across the globe. WHO and many scientists argue that it's not the time to introduce booster vaccines yet since the evidence of their necessity isn't vast, and it is more important to ensure people in low-income countries are vaccinated with primary doses first. In the U.S., the booster program is set to begin in September. The recommended wait is eight months after the first two doses of Pfizer and Moderna vaccines.


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