Nov. 30 (UPI) — COVID-19 infections in people who are fully vaccinated are rare, but more common and severe among those with weaker immune systems, an analysis published Tuesday by the Journal of Medical Economics found.
Among fully vaccinated people included in the study, only 0.08% experienced a “breakthrough” infection, or getting infected and experiencing symptoms despite being immunized, the data showed.
People with weakened immune systems due to underlying health conditions such as cancer represented 18% of study participants, however, they accounted for more than 38% of breakthrough infections.
In addition, these immunocompromised participants made up nearly 60% of all hospitalizations and 100% of deaths caused by breakthrough infections in the fully vaccinated, according to the researchers.
“The results … support the introduction of a third dose of a COVID-19 vaccine to increase protection among the immunocompromised individuals,” co-author Manuela Di Fusco said in a press release.
“While COVID-19 mRNA vaccines help protect people from getting infected and severely ill, the risk of breakthrough infections in fully vaccinated people is not completely eliminated,” said Di Fusco, director of health economics and outcomes research at Pfizer.
Pfizer, along with BioNTech, developed one of the two mRNA-based COVID-19 vaccines available in the United States, with Moderna producing the other one.
The single-dose Johnson & Johnson vaccine, which also is approved in the United States, is made with a different formulation.
All three vaccines offer protection against severe illness from COVID-19 by priming the immune system to fight off the virus, though this protection wanes over time, research indicates.
However, a small number of those immunized still experience symptoms, or so-called “breakthrough” illness, according to data from the Centers for Disease Control and Prevention.
For this study, Di Fusco and her colleagues analyzed the healthcare records of nearly 1.3 million people age 16 and older who had received both doses of the Pfizer vaccine between Dec. 10 and July 8.
Of this group, 225,796, or about 18%, were identified as immunocompromised due to their having advanced HIV/AIDS, cancer, kidney disease, rheumatologic or other inflammatory conditions and other immune conditions or being bone marrow or organ transplant recipients.
Among all people included in the study, 978 breakthrough COVID-19 infections occurred, and 124, or 13%, required hospital treatment, the data showed.
About 38% of all breakthrough cases occurred in people with weakened immune systems and nearly 60% of those hospitalized due to these infections were immunocompromised.
Only two people in the study with breakthrough infections after being fully vaccinated died, and both were immunocompromised, according to the researchers.
“Our study results advance the understanding of post-vaccination outcomes and support recent recommendations to provide a third primary series dose of an mRNA COVID-19 vaccine to patients with weaker immune systems after the initial two doses,” Di Fusco said.
Indeed, similar studies have found an even higher risk for breakthrough infections among people with weakened immune systems.
For example, research published earlier this month by the journal Transplantation found that organ transplant patients have an 82-fold higher risk for breakthrough infection and 485-fold higher risk for hospitalization or death as a result.
“This is a strong reminder that there are vulnerable people all around us who have compromised immune systems, suboptimal responses to the vaccines and higher chances of getting this terrible disease,” Dr. Dorry Segev, co-author of the Transplantion study, told UPI in an email.
“For immunocompromised people, in many cases, two doses are not enough, and we need to keep pushing to understand how to achieve good vaccine responses,” said Segev, vice chair of surgery at Johns Hopkins University in Baltimore, who was not part of the Pfizer study.