Moderate and severely immunocompromised individuals, including people with HIV, cancer, and those who take medicines that suppress the immune system, may be at a higher risk of COVID-19.
All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub for the most recent information on COVID-19.
These individuals are generally at a higher risk of developing severe and persistent illnesses compared with others. They may also lack adequate protection or immunity against coronavirus infection.
This makes them susceptible to infection even after receiving a two-dose primary mRNA COVID-19 vaccine. This is already evident from the significant number of immunocompromised individuals hospitalized for “vaccine breakthrough infections” and fully vaccinated people who still get SARS-CoV-2 infections. An infection with the virus SARS-CoV-2 is what causes COVID-19 in people.
These extra vaccines and boosters can help protect against serious illness and the need for hospitalization due to COVID-19.
All vaccines that currently have approval and authorization in the United States —
However, emerging data suggest that these vaccines are less effective in preventing COVID-19 illness and hospitalization in immunocompromised individuals. These people comprise about
Generally, immunocompromised people seem to be at a higher risk of developing severe forms of COVID-19. A 2021 study found that these individuals are at risk for prolonged infection. Another
Additionally, a 2020 study found that immunocompromised individuals and people with diabetes are more likely to pass on SARS-CoV-2 to others in their households. A 2021 Israel study found that
The CDC recommends moderate to severely immunocompromised people receive a third dose of Pfizer or Moderna, or two shots of the Janssen vaccine, and then an additional two boosters. These may include those with or who have had:
- active or recent treatment for solid tumors or blood cancers
- received a solid-organ or a recent hematopoietic stem cell transplant, a treatment for some cancers and other diseases
- severe primary immunodeficiency, as observable in conditions such as DiGeorge syndrome
- untreated or advanced HIV infections
- treatment with medications that suppress the immune system, such as chemotherapy drugs and high dose corticosteroids
Individuals with chronic conditions associated with varying immunocompetence, such as chronic kidney disease may also need a third primary vaccine dose. And those with other medical conditions and treatments involving varying immunosuppression may also need a third dose.
A person’s healthcare team can assess the degree of immunocompetence and decide whether and when they should receive their third primary dose.
An additional primary dose may prevent serious and life threatening COVID-19 in immunocompromised people who have not developed enough protection from their first two-dose vaccine series.
Studies found that individuals with no detectable antibody response after their first two doses of vaccines, such as solid-organ transplant recipients and
It is important to note that experts cannot directly associate antibody levels with preventing infection. However, research is currently underway to understand this link further.
There is currently limited information on the risks of taking additional doses of the COVID-19 vaccine. Studies about their efficacy, safety, and benefits are currently underway.
All individuals with an appointment for an additional COVID-19 vaccine dose should bring their vaccination cards. These contain relevant information, including the type of vaccine they initially received and when and where they received their initial two doses.
However, if the type of mRNA product is unknown or unavailable, a person may receive any of the two product types for their additional dose. Currently, the
|Vaccine||Age group||Total doses||Second dose||Third dose|
|Pfizer||5–12+||3||21 days after the first dose||at least 28 days after the second dose|
|Moderna||18+||3||28 days after the first dose||at least 28 days after the second dose|
|Janssen||18+||2||Pfizer or Moderna at least 28 days after the first dose||not recommended|
The CDC recommends everyone
The CDC recommends moderately and severely immunocompromised people follow its
|Vaccine||Age||First booster||Second booster|
|Pfizer||5-11||at least 3 months after their third dose||not recommended|
|Pfizer||12+||at least 3 months after their third||at least 4 months after their first booster|
|Moderna||18+||at least 3 months after their third dose||at least 4 months after their first booster|
|Janssen||18+||at least 2 months after their second primary dose||at least 4 months after their first booster|
Adults who received an initial shot of Janssen should have a Pfizer or Moderna second shot at least 28 days later. They can then receive a Pfizer or Moderna booster shot at least 2 months after their second vaccine.
Several studies and trials are underway to assess the effectiveness and safety of vaccine boosters in immunocompromised individuals. A recent nationwide survey found that local and systemic reactions due to the third dose in immunocompromised individuals were the same as in previous vaccines. Additionally, most individuals reported better responses from the third dose than the second.
Trials are also evaluating the effectiveness of mixed-dose vaccine schedules and boosters. A preprint of a 2021 study in Germany found people tolerated a mixed-dose booster vaccination of ChAdOx/BNT well. They also had similar side effects to those observable in same-dose boosters. People also had improved immunity responses in both same-dose and mixed-dose boosters.
A similar 2021 preprint found that heterologous, or mixed, vector-mRNA boosted immune response. This means receiving a ChAdOx1-nCoV-19 vector-vaccine for the initial two-dose series and then an mRNA-vaccine booster yielded favorable protection with manageable side effects.
Another 2021 study preprint looking at heterologous schedules, or using a different vaccine product for the second dose than the first dose, found that these produced higher antibody levels than the licensed vaccine schedule.
The National Institutes of Health (NIH) also states that research shows a person with a mixed vaccine primary and booster shot has antibody levels similar to those who receive the same vaccine for all of their shots.
Additionally, levels of CD4 and CD8 T cells, which are types of immune cells that may help against SARS-CoV-2, rose no matter which vaccine a person received, unless they had a Janssen shot as their first vaccine. However, people who had a Janssen shot already had higher levels of CD8 T cells.
Emerging data suggest current COVID-19 vaccines are less effective in preventing illness and hospitalization in immunocompromised people. Therefore, those who are immunocompromised are at a higher risk of developing severe forms of COVID-19.
This population may wish to ensure that close contacts are up-to-date on their vaccinations. They should also continue to take preventive measures such as regular handwashing, mask-wearing, and maintaining social distancing.
The CDC recommends immunocompromised persons have three primary vaccine doses. Those who are 12 years of age and older should have two additional boosters of an mRNA COVID vaccine. People should receive their first booster at least 3 months after their last primary dose and then a second booster at least 4 months later. Immunocompromised children aged 5–11 years should receive one mRNA COVID vaccine booster at least 3 months after their last primary dose.
Any immunocompromised people interested in COVID-19 booster shots but are unsure of which to receive and when can contact their doctor for further guidance.