COVID-19 vaccine protection decreases over time, especially in older adults and immunocompromised individuals, necessitating additional booster doses to maintain immunity1 2. The Centers for Disease Control and Prevention (CDC) recommends updated COVID-19 vaccination for most adults, with special guidance for those at higher risk of severe disease3 4. Understanding eligibility, timing, and safety of additional bivalent boosters is essential for informed vaccination decisions5 6.
Eligibility for an Additional Bivalent Booster
The Advisory Committee on Immunization Practices (ACIP) recommends updated COVID-19 vaccination for all persons aged 6 months and older7 . However, additional booster doses are specifically advised for adults aged 65 years and older and for individuals with moderate or severe immunocompromise to enhance protection against circulating SARS-CoV-2 variants and severe disease5 7.
“This vote allows people to make the best decisions possible to keep themselves and their loved ones safe from COVID-19. CDC will continue to educate the public on how and when to get their updated vaccinations so they can risk less severe illness and do more of what they love.”
— Dr. Mandy Cohen, Centers for Disease Control and Prevention (CDC) 23
Key eligibility criteria include:
- Adults aged 65 years and older should receive a second dose of the 2024–2025 COVID-19 vaccine at least 6 months after their previous dose, with a minimum interval of 2 months allowed based on individual risk5 74.
- Persons aged 6 months and older with moderate or severe immunocompromise may receive a second dose of the 2024–2025 COVID-19 vaccine 6 months after their last dose, with a minimum interval of 2 months; additional doses beyond two may be given based on shared clinical decision-making5 4.
- For immunocompromised individuals, shared clinical decision-making allows flexibility in timing and number of doses, guided by healthcare providers considering personal risk factors and circumstances5 4.
- Non-mRNA vaccines, such as Novavax (protein subunit) and Janssen (adenovirus vector), remain authorized alternatives for those with contraindications to mRNA vaccines8 94.
- Healthcare providers play a crucial role in advising patients on appropriate booster timing and vaccine type based on medical history10 7.
Vaccination schedules vary depending on prior vaccine history and immune status, with unvaccinated individuals or those who received non-mRNA vaccines requiring tailored dosing intervals4 .
The 2024–2025 COVID-19 vaccines are updated to target currently circulating SARS-CoV-2 strains, including the JN.1 lineage, to provide optimal protection4 .
Considering a Second Bivalent Booster
COVID-19 vaccine effectiveness wanes over time, particularly several months after booster administration, leading to increased susceptibility to infection and severe outcomes1 2. This decline is more pronounced in older adults and immunocompromised persons, who are prioritized for additional booster doses to sustain immunity11 1.
COVID-19 vaccines, including bivalent boosters, have been administered safely to hundreds of millions of people in the U.S., with ongoing monitoring ensuring prompt detection and investigation of any rare adverse events18 22.
Skipping a recommended second bivalent booster can result in diminished immunity and a higher risk of COVID-19 infection, hospitalization, and death12 213. Mortality rates are significantly higher among unvaccinated older adults compared to those who received bivalent boosters14 13. The analogy of waning immunity to fading paint highlights the need for periodic booster doses to maintain immune defense15 .
Key points to consider:
- Vaccine effectiveness against symptomatic infection and severe disease decreases over months, necessitating additional doses for sustained protection1 2.
- Immunocompromised individuals and older adults benefit from booster doses that restore waning immunity and reduce risk of severe COVID-19 outcomes16 11.
- Booster doses help protect against currently circulating variants and reduce the risk of Long COVID5 3.
- Shared clinical decision-making allows immunocompromised persons to receive additional doses based on clinical judgment and personal preference5 4.
- Despite availability, booster uptake remains low, with only about 43% of adults aged 65 and older having received a bivalent booster6 17.
Maintaining up-to-date COVID-19 vaccination is critical for those at higher risk. Booster doses restore protection that wanes over time and reduce hospitalization and death, especially in older adults and immunocompromised persons12 1316.
Safety of Multiple COVID-19 Vaccinations
Extensive safety monitoring of millions of COVID-19 vaccine doses, including bivalent boosters, confirms a strong safety profile with mostly mild and transient side effects18 19. Serious adverse events are rare and are thoroughly investigated through surveillance systems such as the Vaccine Adverse Event Reporting System (VAERS) and v-safe18 19.
The safety profile of bivalent boosters is consistent with previous COVID-19 vaccine doses, supporting their use in older adults and immunocompromised individuals18 20.
Common side effects include:
- Injection site reactions such as pain and swelling, which are the most frequently reported16 18.
- Systemic symptoms like fatigue, headache, and fever, generally mild and short-lived16 18.
- Severe adverse events are uncommon and not necessarily causally related to vaccination18 19.
The bivalent vaccines are designed to provide broader immunity by targeting both the ancestral SARS-CoV-2 strain and Omicron subvariants BA.4 and BA.5, similar to the rationale behind annual influenza vaccination8 2021. This approach aims to maintain population-level protection as the virus evolves20 21.
Healthcare providers should reassure patients about the safety of additional booster doses, especially in high-risk groups, and encourage vaccination to sustain immunity10 18.
