Quick Answer
The CDC currently recommends that people over 50 years old or people over 12 years old who are immunocompromised get a second COVID-19 booster shot at least 4 months after their first booster. However, the ideal timing for a second booster is not yet clear and may depend on individual risk factors and preferences. Speak to your doctor about the risks and benefits of getting a second booster at this time.
When are second boosters recommended?
The CDC currently recommends second COVID-19 booster shots for:
- Adults 50 years and older at least 4 months after their first booster
- People 12 years and older who are moderately or severely immunocompromised at least 4 months after their first booster
These recommendations are based on evidence that protection from the initial booster doses decreases substantially after about 4 months. Getting a second booster restores antibody levels and provides improved protection, especially for higher risk groups.
However, the recommendations are interim and may change as more data becomes available on the need for and timing of additional boosters.
What do experts say about timing?
There is ongoing debate about the ideal timing for second boosters. Some key considerations according to experts:
- Waiting longer between boosters, such as 6-12 months, may trigger a better immune response and provide more durable protection.
- Getting a booster too soon after the previous dose may not boost immunity as effectively.
- Periodic boosting may be needed, especially for high risk groups, due to waning immunity over time.
- Timing boosters to coincide with surges of new variants may provide better protection when it is needed most.
Given these uncertainties, some experts advise a more individualized approach, taking into account a person’s risk factors, previous infections, immune response, and preferences. Speak to your healthcare provider about the advantages and disadvantages of getting a second booster at 4 months or longer.
What are the risks of waiting longer?
The potential risks of waiting longer than 4-6 months for a second booster include:
- Greater risk of infection, symptomatic illness, and complications due to waning immunity.
- Possibly lower protection if infected during periods of higher community transmission.
- Missed opportunity for better protection if boosters are eventually not recommended after longer intervals.
However, for young healthy individuals, the personal risks of severe illness may be low. The interim recommendations are mainly aimed at providing improved protection for higher risk populations.
What factors may influence timing?
Some factors to consider when deciding on timing for a second booster include:
- Age – Older adults have higher risk of severe disease so may benefit from an earlier second booster.
- Immune status – Those who are immunocompromised may need boosters on a shorter interval to maintain protection.
- High risk conditions – Those with medical conditions putting them at higher risk of complications may benefit from earlier boosting.
- Previous infections – Breakthrough infections act like boosters, so timing may be adjusted after infection.
- Time since last vaccine – Longer intervals up to 6-12 months may trigger a stronger immune response.
- Variant outlook – Surges of new variants may warrant timing boosters accordingly.
Discuss your specific situation and risk factors with your healthcare provider to determine the best booster timing for you. Be prepared to adapt as recommendations evolve.
How much additional protection does a second booster provide?
Data on the added protection from a second mRNA booster so far shows:
- 2-4 fold increase in neutralizing antibodies against Omicron BA.1 compared to pre-booster levels.
- Restores efficacy against infection to about 50% from less than 30% prior to the booster.
- About 75% efficacy against severe disease over about 3 months follow-up.
- 64-74% efficacy against COVID-related hospitalization in adults over 60 during periods of Omicron prevalence.
However, exactly how much added protection will be provided and how long it will last is still under investigation. Effectiveness may vary based on individual factors like age, immune status, time since last vaccine, and type of vaccine received.
How long does protection from a second booster last?
It’s not yet clear how durable the protection from a second mRNA booster will be.
Studies so far show:
- Neutralizing antibodies increase rapidly 1 week after the booster then decline after about 2 months.
- Efficacy against infection decreases from about 50% to 30% by 3 months post-booster.
- Immune memory responses may provide longer lasting cellular immunity.
Given the current trajectory, protection is likely to wane substantially by about 4-6 months after the second booster, similar to what was observed after the first booster.
However, the durability could be influenced by use of variant-targeted vaccines, the emergence of new variants, and other factors. More time is needed to fully characterize the longevity of protection.
Should I get a booster now or wait for variant-targeted vaccines?
The FDA recently authorized updated Pfizer and Moderna boosters that target the newer BA.4/BA.5 Omicron subvariants. However, it is unclear if or when these new boosters will be recommended over the original boosters.
Potential advantages of waiting for Omicron-targeted vaccines:
- May provide better protection tailored to currently circulating variants.
- Combines immune response to original and Omicron strains.
- Observation period will provide more data on efficacy and durability.
Potential advantages of getting a booster now:
- Restores waning immunity from previous shots sooner.
- Original boosters still provide good protection against severe disease.
- Avoid unpredictable surges in infections while waiting.
For those at higher risk, getting the additional protection now rather than waiting a few months may be preferable. For younger healthy people, waiting for more data may be a reasonable option.
Conclusion
The optimal timing for COVID-19 boosters is still under investigation. While second boosters are currently recommended for those 50 and older at 4 months after the initial booster, some experts advise waiting longer between boosters may trigger a stronger immune response. Consider your personal risk factors when deciding on timing. Be prepared to adapt recommendations as more data on variant-targeted vaccines and durability of protection emerges. Discuss your individual circumstances with your healthcare provider to determine your best course of action.
When did second COVID boosters get authorized in the US?
| Date | Authorized Groups |
|---|---|
| March 29, 2022 | Second booster for adults 50+ and certain immunocompromised individuals |
| May 19, 2022 | Second booster for adults 50-59 |
| August 12, 2022 | Second booster for adolescents 12-17 who are immunocompromised |
The FDA first authorized second boosters for those 50 and older in March 2022 based on evidence of waning immunity. Additional groups were added over the following months as more safety and efficacy data became available. Timing recommendations currently stand at a minimum of 4 months after the first booster.
How do COVID vaccines and boosters work?
COVID-19 vaccines work by training your immune system to recognize and fight the virus that causes COVID-19. Here is how the primary series and booster shots generate immune protection:
- The first dose primes the immune response, allowing immune cells to detect key parts of the virus.
- The second dose strengthens and further trains virus-fighting antibodies, B cells, and T cells.
- Over time, antibody levels wane and immunity weakens without exposure to the virus.
- Boosters re-expose your immune system to the vaccine, enhancing antibodies and memory responses.
- This restores protective immunity against infection, illness, hospitalization and death.
Booster doses are especially important against variants like Omicron that are more capable of evading the immune protections generated by the original vaccines.
What are the risks and side effects of additional boosters?
So far, data indicates that second booster doses have a safety profile similar to that of the first booster dose. The most commonly reported side effects are:
- Pain, redness or swelling at injection site
- Tiredness
- Headache
- Muscle pain
- Fever
- Chills
- Nausea
- Joint pain
These tend to be mild to moderate in severity and resolve within 1-3 days. Serious side effects like severe allergic reactions, myocarditis, and pericarditis are very rare. There are currently no concerns or safety signals specific to second booster doses.
Which vaccine can be used for the second booster?
The available mRNA vaccines made by Pfizer-BioNTech and Moderna can both be used for second COVID-19 booster shots regardless of which vaccine you received previously. The original and variant-adapted boosters from these companies can also be mixed and matched.
There is not yet data on second booster doses of viral vector vaccines like Johnson and Johnson. Novavax has filed for FDA authorization of its vaccine to be used as a heterologous booster option. For now, mRNA vaccines are preferred for greater effectiveness against current variants. Speak to your doctor about which vaccine is recommended for your second booster.
Will additional boosters be needed in the future?
Many experts believe that additional COVID-19 booster doses will be needed on an ongoing basis, similar to annual flu shots. Several factors are contributing to this assessment:
- Immunity from both vaccination and infection wanes substantially within 6 months.
- New variants with some level of immune evasion continue to emerge.
- The virus is now widely circulating globally and cannot be eradicated.
- Younger and healthier groups benefit less from boosting, so immunity gaps in population will allow continued spread.
However, it remains unclear how frequently boosters will be needed. This depends on the durability of protection from additional doses, future variants, availability of improved next-generation vaccines, and other considerations that will become evident over time.
