- Researchers from an unpublished study have claimed that one-fifth of people who have had COVID-19 do not have a specific type of antibodies and therefore may not have adequate protection against future infections.
- The study tested volunteers with a previous SARS-CoV-2 infection for the presence of a type of antibody that only a natural infection can generate, called core anti-N antibodies.
- Smokers and individuals with pre-existing medical conditions, in particular, would test negative for the antibodies.
- Critics of the study say the presence of this type of antibody is a poor indicator of overall immunity against future COVID-19 infection.
- They also point out that studies based on the main anti-N antibody may underestimate the levels of infection with COVID-19 in the community.
People who have had COVID-19 sometimes claim that they do not need to be vaccinated because their infection gave them immunity to the virus.
But a new study suggests that about a fifth of individuals recovering from COVID-19 may not have adequate protection against future infections.
“Our data shows that the best way to protect yourself and others from COVID-19, even if you’ve had the virus before, is to get two doses of the vaccine and the booster when offered,” said lead scientist Dr. Tim Investigator of the research. , professor of genetic epidemiology at King’s College London in the United Kingdom.
The study found that 19% of people with a previously confirmed infection had no
These antibodies target a protein called the nucleocapsid found in SARS-CoV-2, the virus that causes COVID-19.
Only a natural SARS-CoV-2 infection can generate anti-N antibodies, while vaccines trigger the production of antibodies against the spike protein, which is on the outside of the virus.
The study reported on 8,193 adults who reported a previous SARS-CoV-2 infection – confirmed with a PCR test – using the ZOE COVID smartphone app. Each participant also reported at least one symptom in the following 2 weeks and responded to an invitation to undergo an anti-N antibody test at home.
The researchers did not provide information about the response to their request for additional research.
The scientists behind the app sent out invitations between April 2021 and August 2021. They did not provide information about when the participants registered their positive PCR results.
Overall, 81% of the participants tested positive for anti-N antibodies, while 19% tested negative.
Participants who tested negative were more likely to be smokers and had one or more additional medical conditions or co-morbidities.
Conversely, those who tested positive tended to have more symptoms, or at least one of the classic COVID-19 symptoms of fever, persistent cough and anosmia — a loss of taste and smell.
Among the participants who tested positive, there was no evidence of a decrease in anti-N antibodies up to 9 months after infection. Therefore, it seems that some participants have already registered their positive test in January or February 2021, but no information was given in the press release and blog about this study.
dr. Claire Steves, a scientist involved in the ZOE COVID studies and a senior clinical lecturer at King’s College London, says the research indicates that not everyone who has had COVID-19 maintains their antibody response to the virus.
“This underlines the importance of getting vaccinated, even if you’ve been exposed to the virus,” says Dr. Steves.
“Our data shows that this is especially important for people with other pre-existing health conditions and those who smoke,” she adds.
Scientists speaking to the Science Media Center in London pointed out several shortcomings of the study, which has been published neither as a preprint nor as a peer-reviewed paper.
“These results are quite simplistic and incomplete,” says Dr. Julian Tang, professor of respiratory sciences at the University of Leicester in the UK.
He pointed out that the study does not measure the responses of the participants’ T cells, which play a vital role in the body’s adaptive immune system, in addition to B cells, which produce antibodies.
“T-cell responses have been studied before and can provide immune protection even in the absence of an antibody (B-cell) response — or symptomatic infection,” he said.
In addition, he said the study does not measure a class of antibodies known as IgA in the mucous membranes. These form a first line of defense against infection in the respiratory tract.
dr. Tang also quoted:
While not a study specifically related to anti-N antibody levels, the timing of the sample may have influenced the findings of the ZOE study. They tested only one sample from each participant over a period of at least 9 months from the onset of symptoms.
Finally, he points out that the ZOE study did not test for the presence of antibodies against other proteins in the virus.
“This is why natural infection with viruses generally provides longer and broader immune protection — compared to vaccination,” said Dr. tongs.
“Vaccination after natural infection boosts immunity against that particular vaccine target — but that background, primed level of immunity is still protective to some degree — probably for life — as we’ve seen before with flu,” he added.
dr. Simon Clarke, associate professor of cellular microbiology at the University of Reading in the UK, agreed that testing for anti-N antibodies alone was a major limitation of the ZOE study.
“It remains possible that people had antibodies that were reactive to other coronavirus proteins, which offered some protection against infection or disease, and this is an obvious research question to ask,” he said.
dr. Clarke pointed out that the nucleocapsid protein is located in the core of the virus, unlike surface proteins, such as the spike protein, which the virus uses to infect cells.
“Therefore, it is difficult to envision exactly how antibodies reactive to N protein would act to block the virus interacting with our cells or mark it for destruction by our white blood cells,” he said.
“It could be that someone with low anti-N protein antibodies has a huge amount of anti-spike protein antibodies and some killer T cells, which provides strong protection,” he added.
“The fact that people don’t necessarily make antibodies after [SARS-CoV-2] infection or even after vaccination is well known,” says Dr. Paul Hunter, professor of medicine at the University of East Anglia in the United Kingdom.
He argued that antibodies are not essential for recovery from COVID-19.
He cited a study showing that even people with weakened immune systems — making it difficult for them to produce antibodies — can experience only mild COVID-19.
“Although people with lower anti-spike antibody levels are more at risk for reinfection, there is still some degree of protection after infection even without an antibody response,” he said.
It is difficult to interpret this study in relation to a future infection risk after natural infection, as there is insufficient detail in the press release and blog to determine the degree of bias and effect of other forms of immunity. dr. However, Hunter identifies one important implication of this study that is likely to be robust when published under peer review:
“One of the main implications of this is that those studies that have looked at the prevalence of [antibodies] in a population as an estimate of previous infection […] will likely have significantly underestimated the proportion of people who have already had COVID-19 and recovered.”