The research, commissioned by the British government, indicates people's immune response to COVID-19 reduces over time following infection.
A study conducted in the United Kingdom on immunity against COVID-19 has found that antibodies against the novel coronavirus declined rapidly in the British population during the summer. The study is yet another confirmation on studies which suggest that protection after COVID-19 infection may not be long-lasting.
Scientists at Imperial College London tracked antibody levels in the British population following the first wave of COVID-19 infections in March and April. The study found that antibody prevalence fell from 6 percent of the population around the end of June to just 4.4 percent in September.
The study involved 3,65,000 randomly-selected adults administering at home three rounds of finger-prick tests for coronavirus antibodies between June 20 and September 28. The results showed the number of people with antibodies fell by 26.5 percent over the approximately three-month period.
"We can see the antibodies and we can see them declining and we know that antibodies on their own are quite protective," said Wendy Barclay, Head of Department of Infectious Disease at Imperial College London.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
"On the balance of evidence I would say, with what we know for other coronaviruses, it would look as if immunity declines away at the same rate as antibodies decline away, and that this is an indication of waning immunity at the population level," Barclay said.
Moreover, asymptomatic coronavirus sufferers appear to lose detectable antibodies sooner than people who have exhibited COVID-19 symptoms, according to the study published on October 27.
The findings also suggest the loss of antibodies was slower in 18–24 year-olds compared to those aged 75 and over. The research, commissioned by the British government, indicates people's immune response to COVID-19 reduces over time following infection.
There was no change in the levels of antibodies seen in healthcare workers, possibly due to repeated exposure to the virus.
Barclay said that the rapid waning of antibodies from infection did not necessarily have implications for the efficacy of vaccine candidates currently in clinical trials. "A good vaccine may well be better than natural immunity," she said.
But scientists involved cautioned that a great deal remains unknown about people's long-term antibody response to the virus. "It remains unclear what level of immunity antibodies provide, or for how long this immunity lasts," said Paul Elliott, of Imperial's School of Public Health.
"This very large study has shown that the proportion of people with detectable antibodies is falling over time," said Helen Ward, one of the lead authors. Imperial's findings were released as a pre-print paper, and have not yet been peer-reviewed.
(With inputs from agencies)Click here for Moneycontrol's full coverage of COVID-19 outbreak