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COVID-19 Antibodies Decline Fast

Adults who recover from a mild infection with the novel coronavirus see their COVID-19 antibody levels decline within weeks, according to a recent study.

• Read also: Few Canadian adults have contracted COVID-19, study finds

Researchers at the University of California, Los Angeles followed 34 individuals who contracted the coronavirus for nearly three months, taking blood samples two or three times during this period.

Analysis of samples shows antibody levels drop by half in 73 days on average – barely two and a half months, according to correspondence in the medical journal New England Journal of Medicine.

Most of the patients studied suffered only mild symptoms; only two required supplemental oxygen and none were placed on life support.

The participants were between 21 and 68 years old, for an average age of 43 years.

Concerns about vaccines

“These findings raise concerns that humoral immunity to SARS-CoV-2 may not be long lasting in people with mild disease, who make up the majority of cases,” write the authors of the study.

Antibodies are proteins secreted by the immune system in response to infection. Their function is to recognize and neutralize the pathogen. But their ability to fight the SARS-CoV-2 virus, which causes the COVID-19 disease, has not yet been demonstrated.

However, the body’s immune response cannot be measured only with antibodies.

Immune cells, called T cells, could also play an important protective role against COVID-19.

Despite this, the Californian researchers believe that their findings “call for caution” concerning in particular the concept of collective immunity.

The decrease in antibody levels after a few weeks could “perhaps” even call into question the durability of the vaccines, say these experts.

The case of Sweden

At the end of April, the World Health Organization warned that there is for the moment “no proof” that people who contracted COVID-19 for the first time, and who recover from it, are protected from a second infection.

That hasn’t stopped Swedish health officials recently from asserting that people who have contracted COVID-19 are likely immune for at least six months, even if they don’t develop antibodies.

Remember that this country of ten million inhabitants has been standing apart since the start of the pandemic, with less strict containment rules than elsewhere.

COVID-19 has killed 5,667 in Sweden so far, according to the Johns-Hopkins University tally.

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