COVID-19 Booster For Variants: A Comprehensive Guide


Historically, vaccines undergo extended development timelines. Yet, due to technological advancements like mRNA, vector vaccines, and protein subunit vaccines, COVID-19 boosters were quickly formulated once an understanding of the virus’s genetic sequence and mutations deepened.

Steps in COVID-19 Booster Shot Development in the United States

  1. Preclinical Testing: Potential booster formulations were tested on cells and animals. This helped evaluate efficacy and safety against variants of this infectious disease.
  2. Phase I Trials: A limited number of individuals were given the COVID-19 booster dose to determine its safety and appropriate dosage.
  3. Phase II Trials: The booster dose was tested on a more diverse group, including those of different ages and health conditions. This helped experts understand its safety and immune system stimulation capacity.
  4. Phase III Trials: Widespread testing with thousands to observe the booster’s capacity to augment immunity against the disease long-term.
  5. Approval: Regulatory bodies, such as the FDA, EMA, and WHO assess results, deciding on emergency use or full approval. This helped guide a strategy where people could be vaccinated to prevent COVID-19 variant infections.

For COVID-19 booster shots, the regulatory process was swift, as it built on the foundational knowledge of the original vaccines. The FDA granted Early Use Authorization (EUA) for these boosters, and the CDC assisted in ongoing monitoring and coordination of the data.

Vaccine Manufacturer Brand Name Booster Dose Development Booster Dose Approval
Pfizer-BioNTech Pfizer Comirnaty August 23, 2021 September 24, 2021
Moderna Moderna Spikevax August 13, 2021 September 24, 2021
Johnson & Johnson Johnson & Johnson Janssen November 29, 2021 January 19, 2022
Novavax Novavax Nuvaxovid March 28, 2022 June 28, 2022

Here are some additional details about the development and approval of COVID-19 vaccine booster doses: 

The Pfizer-BioNTech and Moderna booster doses were developed using the same mRNA vaccine technology as the original vaccines. The booster doses contain a higher dose of the same vaccine. 

The Johnson & Johnson booster dose is a different vaccine than the original vaccine. It is a single-dose vaccine that is made with a different technology. 

The Novavax booster dose is also a different vaccine than the original vaccine. It is a two-dose vaccine that is made with a different technology.

Here is a list of COVID-19 variants that the booster shots are known to be effective against as of September 12, 2023:

Vaccine Brand Name COVID-19 Variants
Pfizer-BioNTech Comirnaty Alpha, Beta, Gamma, Delta, Omicron (BA.1), Omicron (BA.2), Omicron (BA.4), Omicron (BA.5)
Moderna Spikevax Alpha, Beta, Gamma, Delta, Omicron (BA.1), Omicron (BA.2), Omicron (BA.4), Omicron (BA.5)
Johnson & Johnson Janssen Alpha, Beta, Gamma, Delta
Novavax Nuvaxovid Alpha, Beta, Gamma, Delta

Please note that this table is not exhaustive and may not include all available COVID-19 vaccine booster doses or COVID-19 variants.

Role of COVID-19 Booster Shots

COVID-19 booster shots amplify the immunity offered by the primary vaccine series. They prime the immune system further against evolving variants of the SARS-CoV-2 virus, especially when initial immunity might wane.

Types of COVID-19 Booster Shots Available in the US

mRNA Boosters: Direct cells to make a piece of the virus’s spike protein, enhancing the immune system’s recognition, especially against variants.

Viral Vector Boosters: Use a different virus to carry the spike protein gene into our cells, promoting a heightened immune response.

Protein Subunit Boosters: Introduce a lab-made piece of the spike protein into the body to stimulate an amplified immune response.

All types of COVID-19 booster shots underwent rigorous clinical trials, proving their efficacy and safety for diverse age groups.

For those contemplating a booster shot, consider factors like the time elapsed since your initial vaccination, your age, and potential exposure risks. Consult with your healthcare provider for guidance.

Effectiveness And Efficacy of COVID-19 Boosters By Type of Booster

Efficacy of COVID-19 vaccines was measured in clinical trials, comparing a vaccine group to a placebo group. 

Effectiveness is measured in real-world studies, where participants are not randomly assigned to groups. The effectiveness rate is calculated by comparing the number of people who get sick in the vaccinated group to the number of people who get sick in the unvaccinated group.

Here is a table summarizing the efficacy by vaccine and brand name:

Vaccine Manufacturer Brand Name Efficacy against symptomatic infection Efficacy against hospitalization Efficacy against death
Pfizer-BioNTech Pfizer Comirnaty 69% (6 months after second dose) 91% (6 months after second dose) 95% (6 months after second dose)
Moderna Moderna Spikevax 76% (6 months after second dose) 93% (6 months after second dose) 97% (6 months after second dose)
Johnson & Johnson Johnson & Johnson Janssen 57% (2 months after single dose) 78% (2 months after single dose) 88% (2 months after single dose)
Novavax Novavax Nuvaxovid 50% (2 months after second dose) 80% (2 months after second dose) 90% (2 months after second dose)

It should be noted that:

The efficacy and effectiveness rates of vaccines can change over time, as the virus mutates and the immune system’s response to the vaccine wanes.

 Other factors, such as age, underlying health conditions, and the timing of vaccination, can also affect the efficacy and effectiveness of vaccines.

The efficacy and effectiveness of COVID-19 vaccine booster doses can vary depending on the vaccine, the time since the initial vaccination series, and the variant of the virus.

The efficacy and effectiveness of COVID-19 vaccine booster doses are generally higher against symptomatic infection than against hospitalization or death.

The efficacy and effectiveness of COVID-19 vaccine booster doses also tend to decline over time.

Side Effects of Booster Doses

Like the initial shots, boosters can cause mild side effects such as soreness at the injection site, fatigue, and mild fever. They are short-lived and indicate the body’s immune system is responding.

Access to COVID-19 Booster Shots

Booster doses are available at various locations, such as:

– Doctor’s offices

– Pharmacies

– Community health centers

– Vaccination clinics

Check the Centers for Disease Control and Prevention (CDC) website for the latest guidelines and to find a nearby booster shot location. The FDA approves Booster Doses under the EUA process for all new and potentially serious COVID-19 variants.

All COVID-19 immunization schedules have been updated by the CDC to make sure that the vaccination includes booster doses for coronavirus vaccines. This is true for vaccination for children and for adults.

The development and approval of COVID-19 booster shots underscore the global scientific community’s commitment to combating this pandemic. They enhance immunity against emerging variants.

As of September 12, 2023, the following are the variants of COVID-19 that are circulating:

  • BA.2.75 (Pirola): This is a subvariant of BA.2, which was the dominant variant in the spring of 2022. BA.2.75 is more transmissible than BA.2 and has been shown to evade the immune system more easily.
  • BA.4 and BA.5: These are subvariants of BA.2 that are also more transmissible than BA.2. BA.4 and BA.5 have been shown to cause more severe disease than BA.2.
  • XE: This is a recombinant variant that is a combination of BA.1 and BA.2. XE is more transmissible than BA.2 but does not appear to cause more severe disease.
  • XD: This is a recombinant variant that is a combination of BA.1 and BA.2.12.1. XD is more transmissible than BA.2 but does not appear to cause more severe disease.

The World Health Organization (WHO) is monitoring these variants and will continue to update its recommendations on vaccination and other measures to protect against COVID-19.


How long after my initial vaccination series should I get a booster shot?

The CDC recommends that everyone ages 6 months and older get a booster shot at least 5 months after their primary vaccination series. People who are moderately or severely immunocompromised may need to get a booster shot sooner.

Which COVID-19 booster shot should I get?

The CDC recommends that everyone ages 18 and older get an updated (bivalent) COVID-19 booster shot. The bivalent booster shots target the original COVID-19 virus strain as well as the Omicron variant.

Children ages 6 months to 4 years can get either a bivalent or monovalent (original strain only) COVID-19 booster shot. Children ages 5 to 11 can get a bivalent COVID-19 booster shot.

Can I mix and match COVID-19 booster shots?

Yes, it is safe and effective to mix and match COVID-19 booster shots. You can get any of the available COVID-19 booster shots, regardless of which vaccine you received for your primary vaccination series.

What are the side effects of COVID-19 booster shots?

The most common side effects of COVID-19 booster shots are mild and go away on their own within a few days. Side effects can include:

  • Pain, redness, and swelling at the injection site
  • Fatigue
  • Headache
  • Muscle pain
  • Chills
  • Fever
  • Nausea
  • Vomiting

Rare side effects, such as myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart), have also been reported. However, these side effects are extremely rare, and the benefits of the vaccine far outweigh the risks.

If I have already had COVID-19, do I still need a booster shot?

Yes, even if you have already had COVID-19, you still need a booster shot. Booster shots provide additional protection against the virus, especially against new variants.

If I am pregnant or breastfeeding, can I get a COVID-19 booster shot?

Yes, COVID-19 booster shots are safe and effective for pregnant and breastfeeding women. The CDC recommends that all pregnant and breastfeeding women get a booster shot.

What should I do if I have questions or concerns about COVID-19 booster shots?

If you have any questions or concerns about COVID-19 booster shots, talk to your doctor. They can help you decide if getting a booster shot is right for you.

Protect yourself from most COVID-19 variants. Get a booster shot nao!

Disclaimer: The information presented in this article is intended for general informational purposes only and should not be considered, construed or interpreted as legal or professional advice, guidance or opinion.

Book an appointment with one of our therapists today.

Protect yourself from most COVID-19 variants. Get a booster shot nao!