COVER STORY/THE

long the immunity would protect from COVID-19. Other viruses like the flu mutate over time. So antibodies from a previous infection provide protection for less than a year. In case of COVID-19, many patients who tested negative after treatment are testing positive again. As per one theory, these people getting reinfected might have developed low immunity during the first round of infection. But there is no conclusive evidence on this. When researchers from China tried to reinfect the rhesus monkeys recovered from COVID-19 infection, they did not succeed. The monkeys developed immunity against the disease, says a study published on preprint server

on March 13. However, researchers at Fudan University, Shanghai, who studied blood samples from COVID-19 patients released after treatment, found nearly a third had low levels of antibodies. In some patients, antibodies could not be detected.

A review by the Norwegian Institute of Public Health has also found limited evidence on immunity after infection with SARS-cov-2. “Two studies showed sustainable immunoglobulin G (IgG is an antibody) levels one to two years after SARS-cov

infection, but it is uncertain whether this finding can be generalised to SARS-CoV-2,”

notes the document published in April.

A paper published in on May 3, however, sheds some light on how antibodies behave in people who had recovered from COVID-19. It compared the immune responses of 14 patients—eight recently discharged with six follow-up patients. When compared with healthy controls, all recovered patients had higher levels of antibodies against COVID-19. But when compared among themselves, newly discharged patients had more antibodies than follow-up patients. But for how long would this immunity last? Will they get reinfected if exposed to high quantities of virus or their physical state weaken? Scientists do not have answers to these probing questions so far.

It seems we have to live with the virus for some time even after a vaccine is ready.

BESIDES, THERE IS NO EVIDENCE TO SHOW HOW LONG THE IMMUNITY WOULD PROTECT FROM COVID-19. OTHER VIRUSES LIKE THE FLU MUTATE OVER TIME. SO ANTIBODIES FROM A PREVIOUS INFECTION PROVIDE PROTECTION FOR LESS THAN A YEAR

Vaccines do not provide 100 per cent immunity. Flu vaccine, for one, is 59 per cent effective in adults and 27 per cent in keeping a person out of a hospital. A 2012 review says BCG vaccine, primarily used against tuberculosis, was 60 per cent effective in the first five years after inoculation. The effectiveness decreased to 56 per cent between five and 10 years and to 46 per cent for up to 15 years. But vaccines against diphtheria are effective.

The COVID-19 vaccine has been put on a fast track and there are chances that it might not be tested very robustly. This can pose a serious risk. In an interview with US-based natural health activist Joseph Mercola, Robert Kennedy Jr, an environmental lawyer and anti-vaxxer, narrates the problems with vaccines against coronavirus. He says they trigger the production of two kinds of antibodies. While neutralising antibodies help fight the disease, the binding ones make the body more vulnerable. In 2012, four vaccines were tested on ferrets who showed good antibody response. But when they were exposed to the wild virus, they died. This again happened in 2014 when dengue vaccine DENVax was administered on children in the Philippines. When they got infected with dengue, 600 of them died.

However, some communities may have an advantage over others when it comes to immunity. This natural defence mechanism of the body trains itself and evolves as people get constantly exposed to pathogens. Being challenged daily with diseases like tuberculosis, malaria, dengue and chikungunya, Indians are more immune to infections compared to several other nationals. There is also evidence that Indians have evolved to gain more genes that protect them against viral infections.

“These genes enable natural killer (NK) cells, a type of white blood cells in our body that provide a first line of defense against viral infections,” says Rajalingam Raja, director of Immunogenetics and Transplantation Laboratory at the University of California in San Francisco,