A new study, published today, shows COVID-19 Breakthrough infections are more common and severe among immunocompromised people.

COVID-19 Breakthrough infections were three times more common in people with weakened immune systems, highlighting the need for greater doses in certain groups.

Breakthrough COVID-19 infections are rare in ‘fully’ vaccinated people, but are more common and severe in individuals with weak immune systems, according to a real-world retrospective cohort study covering over 1.2 million people.

Researchers from Pfizer, which co-developed [with BioNTech] one of three currently available COVID-19 vaccines in the United States, led the study, which was published today in the Journal of Medical Economics.

After reviewing medical records, the researchers discovered that just 0.08 percent of thoroughly vaccinated people developed a breakthrough infection between December 10, 2020, and July 8, 2021. Despite the fact that immunocompromised people made up only 18% of those evaluated, they were responsible for almost 38% of infections, nearly 60% of all hospitalizations, and 100% of fatalities.

The proportion of participants with breakthrough infections was three times greater (0.18 percent) among immunocompromised people than among non-immunocompromised people in the control group (0.06 percent).

“The results supplement other real-world studies, and support the introduction of a third dose of a COVID-19 vaccine to increase protection among the immunocompromised individuals,” said Manuela Di Fusco, lead author from the Pfizer Health Economics and Outcomes Research team.

“Several countries are currently experiencing a resurgence of SARS-CoV-2 infections despite the rollout of mass vaccination programmes. 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.”

The Pfizer trial examined at breakthrough infections among those with and without a compromised immune system after they received two doses of the Pfizer/BioNTech (BNT162b2) COVID-19 mRNA vaccine in the US population.

The researchers examined the medical records of 1,277,747 patients aged 16 and above who received two doses of the BNT162b2 COVID-19 mRNA vaccine between December 10, 2020 and July 8, 2021, using a large database of US healthcare administrative data.

Immunocompromised people included those with severe HIV/AIDS, cancer, kidney disease, rheumatologic or other inflammatory disorders, other immunological conditions, and bone marrow or organ transplant recipients, accounting for 225,796 (17.7%) of the total.

The findings of the investigation revealed:

• There were 978 (0.08 percent) breakthrough infections among 1,176,907 completely vaccinated people who were followed for at least two weeks following the second dose.
• A total of 124 (12.7%) of these breakthrough infections needed hospitalization. 74 of them (59.7%) were immunocompromised, and two of them died (both immunocompromised).
• Immunocompromised people accounted for 2% of all breakthrough infections (374 out of 978).

“While the study leveraged a large dataset that has been previously used for healthcare research in the US, the findings should be interpreted in the context of multiple limitations, including coding accuracy and data representativeness beyond the study period” said Di Fusco.

The US Food and Drug Administration (FDA) approved an additional dose of an approved COVID-19 mRNA vaccine in certain immunocompromised individuals on August 12, 2021, and the Centers for Disease Control and Prevention (CDC) recommended that people who are moderately to severely immunocompromised receive an additional dose of the COVID-19 vaccine.

The Joint Committee on Immunization and Immunization (JCVI) of the United Kingdom recommended that adults over the age of 12 who have severely weakened immune systems receive a third dose of mRNA vaccine as part of their primary vaccination schedule on September 1, 2021.

Due to an increased risk of breakthrough infections following regular immunization, the World Health Organization (WHO) recommended that patients with weak immune systems take an additional dose of COVID-19 vaccine on October 11, 2021.

“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”, added Di Fusco.

Despite accounting for only 2.7 percent of the adult population in the United States, approximately half of the vaccinated patients hospitalized with breakthrough COVID-19 infections were immunocompromised as of July 2021.

Source: 10.1080/13696998.2021.2002063

Image Credit: Getty

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