A woman in a protective mask walks through the Brixton market in South London, as the UK continues to be blocked to help curb the spread of the coronavirus.
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Immunity to Covid-19 could last only a few months, according to a UK study that casts doubt on the longevity of potential coronavirus vaccines.
Antibody responses to the coronavirus may peak three weeks after the initial onset of symptoms, but then begin to decline after just 2-3 months, researchers from Kings College London found.
The study, published Saturday on the MedRxiv preprint server and not yet peer-reviewed, examined the antibody levels of 64 patients and six health workers who had tested positive for the virus at the Guy and St Thomas NHS Foundation. (which runs several London hospitals) between March and June. It also monitored 31 additional staff members who volunteered to be tested for antibodies regularly.
The researchers found that the levels of antibodies that can fight the coronavirus peaked three weeks after the onset of symptoms, but then decreased. While 60% of the people evaluated in the study had a “potent” level of antibodies after an average of 23 days after the first onset of symptoms, 65 days after the first signs of symptoms, only 16.7% of those analyzed had this “potent” level of antibodies.
Antibody levels were higher in patients who had more severe disease, although it is not clear why, KCL noted, and some people who developed antibodies were asymptomatic.
The researchers noted that their study found that the antibody response to Covid-19 was similar to that of other human coronaviruses, such as SARS (severe acute respiratory syndrome) and seasonal coronaviruses associated with common colds, in which the antibody response of an individual tends to “decreased over time, from as little as 12 weeks to 12-34 months after infection.”
The study was led by Dr. Katie Doores of the KCL School of Immunology and Microbial Sciences. Commenting on the research, he said he notes that the responses of antibodies to SARS-CoV-2 (or “severe acute respiratory syndrome coronavirus 2,” the virus that causes Covid-19 disease) circulating in the blood are decreasing. after infection and further research is needed to determine the level of antibodies needed to protect against infection.
“We need to continue measuring the antibody responses in these individuals to see if the antibody titers continue to drop or stabilize to a stable state,” he said. Antibody titers refer to the presence and amount of antibodies in a person’s blood.
Research questions how much protection people with the coronavirus have against subsequent reinfection, and the durability of any potential vaccine..
Officials from the World Health Organization said Monday that patients recovering from Covid-19 could re-contract the coronavirus, citing similar studies suggesting that immunity may decline after a few months.
Dr. Maria Van Kerkhove, head of the WHO’s emerging diseases unit, said patients “have a certain level of immune response.”
Speaking at a press conference at the organization’s headquarters in Geneva, he added, “What we don’t know is how strong that protection is and how long that protection will last.”
“So there are a number of ongoing studies that are trying to answer these questions,” he said.
Meanwhile, a peer-reviewed study published in the Lancet medical journal last week stated that Covid-19 antibodies in the Spanish population were “insufficient to provide herd immunity”, which refers to when a population is given allows some exposure to the virus to build immunity among the general population.
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