CDC recommends additional dose of mRNA COVID-19 vaccine in moderately to severely immunocompromised people

Reviewed by Emily Henderson, B.Sc.Aug 13 2021

Today, I signed CDC's Advisory Committee on Immunization Practices' (ACIP) recommendation that endorsed the use of an additional dose of COVID-19 vaccine for people with moderately to severely compromised immune systems after an initial two-dose vaccine series.

This official CDC recommendation -; which follows FDA's decision to amend the emergency use authorizations of the vaccines -; is an important step in ensuring everyone, including those most vulnerable to COVID-19, can get as much protection as possible from COVID-19 vaccination.

Emerging data suggest some people with moderately to severely compromised immune systems do not always build the same level of immunity compared to people who are not immunocompromised. In addition, in small studiespdf icon, fully vaccinated immunocompromised people have accounted for a large proportion of hospitalized breakthrough cases (40-44%). Immunocompromised people who are infected with SARS CoV-2 are also more likely to transmit the viruspdf icon to household contacts.

While people who are immunocompromised make up about 3% of the U.S. adult population, they are especially vulnerable to COVID-19 because they are more at risk of serious, prolonged illness. Included in CDC's recommendation are people with a range of conditions, such as recipients of organ or stem cell transplants, people with advanced or untreated HIV infection, active recipients of treatment for cancer, people who are taking some medications that weaken the immune system, and others. A full list of conditions can be found on CDC's website.

The additional dose of an mRNA COVID-19 vaccine should be the same vaccine as the initial series and administered at least four weeks after completing a primary mRNA COVID-19 vaccine series. While vaccination is likely to increase protection in this population, even after vaccination, people who are immunocompromised should continue follow current prevention measures (including wearing a mask, staying 6 feet apart from others they do not live with, and avoiding crowds and poorly ventilated indoor spaces) to protect themselves and those around them against COVID-19 until advised otherwise by their healthcare provider. CDC does not recommend additional doses or booster shots for any other population at this time.

At a time when the Delta variant is surging, an additional vaccine dose for some people with weakened immune systems could help prevent serious and possibly life-threatening COVID-19 cases within this population.