The antibodies produced by people infected with covid-19 over 50 years of age have a higher degree of protection than younger adults, according to a study carried out by the University of Montreal (Canada), which sought to find out whether the natural infection or the vaccination led to the generation of more protective antibodies.
The research team, led by Joelle Pelletier and Jean-François Masson, both professors in the Department of Chemistry at the University of Montreal, notes that those who received the Pfizer-BioNTech or AstraZeneca vaccine had antibody levels that were significantly higher than those of infected people.
These antibodies were also effective against the Delta variant, which was not present in Quebec when the samples were collected in 2020, notes the study that has been published in ‘Scientific Reports’.
Masson, a specialist in biomedical instruments, and Pelletier, an expert in protein chemistry, were interested in a poorly studied group: people who had been infected with SARS-CoV-2 but were not hospitalized as a result of the infection. Consequently, the Center hospitalier de l’Université Laval recruited 32 non-hospitalized COVID-19 positive Canadian adults 14 to 21 days after being diagnosed by PCR testing. This was in 2020, before the Beta, Delta and Gamma variants emerged.
"Everyone who had been infected produced antibodies, but older people produced more than adults under 50. Also, the antibodies were still present in his bloodstream 16 weeks after his diagnosis."explains Masson.
Antibodies produced after infection by the strain "native" original virus also reacted to the SARS-CoV-2 variants that emerged in later waves, namely Beta (South Africa), Delta (India) and Gamma (Brazil), but to a lesser extent: a reduction from 30 to 50 percent.
"But the result that surprised us the most was that antibodies produced by naturally infected people aged 50 and over provided a higher degree of protection than adults under 50 years of age.", has pointed out Pelletier.
"This was determined by measuring the ability of antibodies to inhibit the interaction of the Delta variant spike protein with the ACE-2 receptor in human cells, which is how we become infected. We do not observe the same phenomenon with the other variants", has added.
When a person who has had a mild case of COVID is vaccinated, the level of antibodies in the blood doubles compared to an unvaccinated person who has been infected with the virus. Your antibodies can also better prevent the pico-ACE-2 interaction.
"But what is even more interesting is that we have samples from an individual under the age of 49 whose infection did not produce antibodies that inhibit the pico-ACE-2 interaction, unlike vaccination. This suggests that vaccination increases protection against the Delta variant among people previously infected with the native strain."Masson notes.
Both scientists believe that more research should be done to determine the best combination to maintain the most effective level of antibodies reactive to all variants of the virus.
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