A study yesterday in the Journal of Infection shows that hybrid immunity from both a fourth vaccination dose and previous COVID-19 illnesses may offer protection against developing long COVID, or post-COVID condition (PCC).
The study is based on 109,707 participant surveys collected about health history and self-reported post-infection symptoms in the German National Cohort. More than 80% of the participants had received three or more COVID-19 vaccinations.
Of the 60% of participants who said they had had a previous COVID-19 infection, 35% reported persistent symptoms 4 to 12 months after infection. Of those, 23% reported "high PCC," which means nine or more symptoms.
Omicron associated with less long COVID
Virus variant type had the greatest influence on developing long COVID. "Any PCC occurred in around 7% after an infection during the Omicron phase for those with a previous infection and in 47% after initial infection with the Wildtype virus," the authors wrote.
The risk of developing any PCC after a second infection if PCC did not follow a first infection was substantially lower compared to after the first infection, resulting in a long-term risk reduction of around 50%, the authors said.
But the risk of developing long COVID was higher in people who were infected less than 3 months following a vaccination, but approximately 50% compared to those who were infected 4 to 6 months after vaccination.
Our findings indicate that the risk of developing PCC was strongly reduced for the second SARS-CoV-2 infection
"Our findings indicate that the risk of developing PCC was strongly reduced for the second SARS-CoV-2 infection, if the first infection did not result in PCC," the authors concluded. "It is possible that the occurrence of breakthrough infections shortly after vaccination is linked to a specific vulnerability of the individual towards PCC, and the apparent protection actually results from confounding."