Sept. 3 (UPI) — People who had severe COVID-19 and later are vaccinated against the virus may be at lower risk for subsequent severe infections with new strains, such as the Delta variant, than those who had milder illnesses, a study published Friday by Science Advances found.
Blood samples collected from COVID-19 patients and fully vaccinated healthcare workers produced reduced immune responses to the Alpha, or U.K., variant, as well as the Beta and Gamma strains, which first were identified in South Africa and Brazil, the researchers said.
The original virus originated in Wuhan, China.
However, blood from those vaccinated against the virus, as well as those with severe enough COVID-19 to require hospitalization, still showed evidence of an adequate immune response to fight off the new strains.
However, blood from patients who had experienced mild COVID-19 infections had lower immune responses to the original virus and often showed no response at all to the Beta and Gamma variants.
“We see that people that experienced mild COVID-19 oftentimes do not have sufficient antibody levels to recognize viral variants and thus would likely need a vaccine to boost their immune response to the coronavirus and its variants,” study co-author Tom Caniels told UPI in an email.
Antibodies are cells produced by the immune system to fight off viruses, and COVID-19 vaccines are designed to bolster their production, said Caniels, a doctoral student in microbiology at the University Medical Centers in Amsterdam.
“It was already known that vaccines protect very well, yet here we show this protection likely carries over to infection with viral variants, as well,” he said.
Although the COVID-19 vaccines currently available in the United States — from Johnson & Johnson, Moderna and Pfizer-BioNTech — are believed to offer 80% to 90% protection against the original Wuhan strain of the coronavirus, they may be less effective against new variants, including Delta, which now is the dominant one nationally.
For this study, Caniels and his colleagues assessed antibody levels in blood samples collected from 69 hospitalized and non-hospitalized COVID-19 patients in the Netherlands and 50 healthcare workers who had received both doses of the two-shot Pfizer-BioNTech vaccine.
Blood samples were collected from participants with COVID-19 four to six weeks after symptom onset, the researchers said.
Antibody levels were higher in patients hospitalized with COVID-19 compared to non-hospitalized patients, the data showed.
They were high enough in hospitalized patients to fight off reinfection with the Beta variant just as efficiently as those who were fully vaccinated, the researchers said.
Nearly 40% of the non-hospitalized COVID-19 patients in the study did not produce enough antibodies to ward off the Beta strain, according to the researchers.
“We observed that people with high antibody levels — those who have had severe COVID-19 or those who are fully vaccinated — generally recognize viral variants better,” Caniels said.
“Having more antibodies translates into recognizing viral variants better, which is why it’s important that people that have experienced only mild COVID-19 get their antibody levels up to be able to recognize viral variants,” he said.