Older people may generate more natural immunity from COVID-19 infection than younger adults, a new study suggests.
Researchers at the Université de Montréal, in Canada, found that antibody levels among people aged 50 and older were higher than in those aged 49 and younger.
The team also found that people who receive the Pfizer-BioNTech or AstraZeneca Covid vaccines are more protected from the virus than those relying on natural immunity alone.
The immunity from previous infection is still effective against different strains of the virus, though, including the highly contagious Delta variant.
Results of the study surprised researchers, and they cannot determine why older people seem to have stronger immune responses to infection.
Researchers found that people over the age of 50 were generating more natural immunity to COVID-19 after contracting the virus. Their immunity was effective against the native virus strain (black), the Beta variant (red), the Delta variant (blue) and the Gamma variant (gray)
‘Everyone who had been infected produced antibodies, but older people produced more than adults under 50 years of age,’ said Jean-François Masson, a chemistry professor at the university and co-lead researcher of the study, said in a statement.
‘In addition, antibodies were still present in their bloodstream 16 weeks after their diagnosis.’
Researchers, who published their findings in Scientific Reports on Monday, gathered data from 32 Covid survivors whose illness did not require hospitalization.
Participants were split into groups based on their age, and then had samples collected to determine their antibody levels at four and 16 weeks after infection.
Each of the participants were infected with the virus at some point in 2020, and had contracted the native strain of the virus that originated in Wuhan, China.
They were found to have generated some natural immunity to the virus after infection, and researchers determined that the antibodies are effective against several variants including Beta, which originated in South Africa; Delta, originated in India’ and Gamma, which originated in Germany.
Antibodies generated by the original strain of the virus are still less effective against variants than they are against the original.
While natural immunity can protect a person from repeat Covid infection, researchers found the vaccine was more effective. Pictured: A man in San Diego, California, is tested for COVID-19
Researchers determined this by testing the antibodies’ ability to to stop the spike protein of the virus from interacting with the ACE-2 receptor of human cells.
That interaction is how a person becomes infected with the virus, and neutralizing the action is how antibodies prevent it.
Antibodies generated by older people showed more ability to prevent the interaction.
‘The result that surprised us the most was that antibodies produced by naturally infected individuals 50 and older provided a greater degree of protection than adults below 50,’ said Joelle Pelletier, co-lead author of the study and professor at the university, said in a statement.
‘This was determined by measuring the antibodies’ capacity to inhibit the interaction of the Delta variant’s spike protein with the ACE-2 receptor in human cells, which is how we become infected.’
The best protection from all strains of Covid is vaccination, the researchers stress.
A person who previously had COVID-19, and then gets vaccinated, will have their antibody count double as a result.
Antibodies provided by the Pfizer and AstraZeneca vaccines were also found to be more effective at preventing infection.
Researchers recommend that all people, even young people who previously recovered from the virus, get the jab when they can.
‘We have samples from an individual younger than 49 whose infection didn’t produce antibodies inhibiting spike-ACE-2 interaction, unlike vaccination,’ Pelletier said.
‘This suggests that vaccination increases protection against the Delta variant among people previously infected by the native strain.’
The AstraZeneca vaccine is not available in the U.S., but has been distributed in Canada.
According to official data, 77 percent of Canadian adults have received at least one shot of a COVID-19 vaccine, and 74 percent are fully vaccinated.
The nation is on pace with its American neighbors, where 80 percent of adults have received at least one shot and 70 percent are fully vaccinated.