COVID-19: Which offers better protection—an infection, a booster or something else?

Remember back in December 2021 and January 2022?While booster doses of the COVID-19 vaccine were being administered—primarily to seniors and healthcare workers, then to the entire population—the fifth wave was sweeping through the country via the Omicron variant. Public health recommended people who received two doses of vaccine and had a recent infection wait three months before getting their booster, on the principle that they benefitted from the same level of protection as with three doses of vaccine. This recommendation would become the starting point for research conducted in Montreal by Dr. Hélène Decaluwe, in close collaboration with the team led by Dr. Jennifer Gommerman, from the University of Toronto. Read: Practice statements on helping patients with post COVID-19 condition“We wondered if it was relevant to wait three months and if an infection protects as much as a vaccine booster,” said Dr. Decaluwe, the pediatric immunologist at CHU Sainte-Justine Hospital in Montreal, who participated at the time in the Working Group on Immunity against COVID-19 and the Canadian research consortium on COVID-19 variants, CoVaRR-Net.Immune responseThe researchers had blood samples from two “quite exceptional” cohorts. The first consisted of 52 Montreal healthcare workers infected at the very beginning of the pandemic who then received their two doses of vaccine. The second was comprised of 71 Torontonians who had also been doubly vaccinated, but without prior infection. The scientists then distinguished people infected with the Omicron variant from those who had received a booster vaccination. For each group, the team analyzed the immune response, focusing on the antibodies produced, the individual's ability to neutralize the virus and the cellular immune memory response. Their results, published recently in the journal Mucosal Immunology, show that in previously vaccinated people, “the extent and magnitude of T cell responses were comparable in the two contexts.” On the other hand, the researchers “observed big differences” in the level of neutralizing antibodies in people who had never had the virus before their vaccination.Read: B.C. launches spring COVID-19 booster program, targeting vulnerable and unvaccinated“The Omicron infection had a greater potential to produce these neutralizing antibodies than the third dose of vaccine,” said Dr. Decaluwe. In addition, while the vaccination booster had a limited impact on the IgA antibodies in the nasal and salivary mucous membranes, infection by Omicron increased their production, “which promotes more effective protection against the virus by preventing it from penetrating in the body."Mimic local infectionThe immunologist deduced that a combined approach of intramuscular and mucosal vaccines could prevent serious COVID-19 infections and reduce transmission. “Our results indeed suggest that a booster dose using an intranasal vaccine, which would mimic a local infection, would be relevant to re-stimulate the mucosal immune system and provide a barrier to SARS-CoV-2,” she added. However, she did not know how long the protection offered by stimulation of the nasal wall lasts, compared to that of the booster.Intranasal vaccination already exists, particularly against influenza. For COVID-19, several nasal vaccine candidates are under development and are currently undergoing clinical trials. “We do not yet have solid data, but there is hope,” said Dr. Decaluwe, emphasizing that there are still many unanswered questions regarding their effectiveness and their possible combination with intramuscular vaccines.

COVID-19: Which offers better protection—an infection, a booster or something else?

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