Covid infections in fully vaccinated ‘more severe in the immunocompromised’

Covid infections in the fully vaccinated are ‘more severe in the immunocompromised’, a study reported (Yui Mok/PA)

Coronavirus infections in fully-vaccinated people are rare but are more common and severe in people with weaker immune systems, a new study has suggested.

Researchers analysed healthcare records and found that only 0.08% of people in their fully-vaccinated pool experienced a breakthrough infection between December 10, 2020 and July 8, 2021.

They also found that while immunocompromised individuals represented 18% of those studied, they accounted for more than 38% of infections, nearly 60% of all hospital admissions, and 100% of deaths.

According to the study, the proportion of people with breakthrough infections was three times higher among immunocompromised individuals (0.18%) than among the reference group of non-immunocompromised people (0.06%).

Manuela Di Fusco, lead author from the Pfizer Health economics and outcomes research team, said: “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.

“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.”

Identifying individuals in the US population who had received two doses of the Pfizer/BioNTech vaccine, the Pfizer study looked to examine breakthrough infections among those with and without a weakened immune system.

The team analysed healthcare records of 1,277,747 people aged 16 or over who had received two doses of the jab.

In this group, 225,796 (17.7%) were identified as immunocompromised – including people with advanced HIV/Aids, cancer, kidney disease, rheumatologic or other inflammatory conditions, other immune conditions, and bone marrow or organ transplant recipients.

Ms Di Fusco added: “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.”

The research is published in the Journal of Medical Economics.