The Centers for Disease Control and Prevention (CDC) recently announced that individuals who are moderately or severely immunocompromised may need to get a fourth COVID-19 vaccine injection at least six months after their third dose.
The CDC's new guidelines state that those who are moderately and severely immunocompromised should receive their third shot at least 28 days after their second dose and may follow up with a fourth dose after six months. "In such situations, people who are moderately and severely immunocompromised may receive a total of four COVID-19 vaccine doses," the CDC said.
Moderately to severely immunocompromised individuals refer to those who are in active cancer treatment for cancers of the blood or tumors. They also include organ transplant patients and stem cell recipients, people with advanced HIV and others who take high doses of corticosteroids or other immunosuppressants. (Related: Coronavirus booster shots: Boosting immunity or profits?)
The CDC believes that there are around 9 million immunocompromised individuals in the U.S. who qualify in these categories.
CDC recommends Pfizer-BioNTech or Moderna vaccines for immunocompromised
The CDC recommends immunocompromised individuals to be vaccinated with either the Pfizer-BioNTech or Moderna mRNA doses. However, the third shot is not considered a booster, but rather a part of their primary vaccination series.
Those with compromised immune systems do not mount adequate immune responses following the first two vaccinations, and the purpose of the third dose is to raise their immunity levels to what is usually seen in healthy individuals after two doses.
The fourth dose, on the other hand, is set to combat waning immunity and will serve the same purpose as a booster dose for those without immune system deficiencies six months after their initial vaccination.
"We know that six months after you reached a good level of protection, your protection has waned … and we need to boost that. That's for people with normal immune systems and people who are immunocompromised," said Dr. Dorry Segev, professor of surgery at Johns Hopkins University.
An estimated 2.7 percent of adults in the U.S. are considered immunocompromised, but not all of them will need a fourth dose.
The change in its clinical considerations comes less than a week after an advisory committee to the CDC officially endorsed a booster shot for the Moderna and J&J vaccines. The question of how and whether or not to provide a booster dose to immunocompromised individuals who may have already received their third dose was brought up during the advisory committee's meeting.
Dr. Doran Fink, the clinical deputy director of the division of vaccines and related products for the Food and Drug Administration (FDA), ??told the committee that under the emergency use authorization, someone who is immunocompromised and has received a third primary series dose would be eligible for the fourth dose six months later.
CDC spokesperson Kristen Norlund said that the clinical considerations were already updated as a result of the discussions.
While the decision is logical from a scientific standpoint, Dr. Balazs Halmos, director of thoracic oncology at the Montefiore Einstein Cancer Center in New York City, said that it is not necessarily data-driven.
Dr. Matt Kalaycio from the department of hematology and medical oncology at Cleveland Clinic agreed, saying that he is unaware of data supporting a fourth dose in immunocompromised patients. "It is unclear to me on which data the CDC is leaning to reach their conclusion," he said.
However, because the third dose for immunocompromised patients was just authorized in August, he believes that the recommended fourth shot is not imminent at the moment.
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