Kerala

Number of COVID-19 infected beyond what was ever seen before: health expert

Dr. Rajeev Jayadevan, vice chairman, Research Cell, Indian Medical Association, Kerala

Dr. Rajeev Jayadevan, vice chairman, Research Cell, Indian Medical Association, Kerala

The Omicron wave has taken hold of the State. In our ongoing weekly COVID meetings in Kochi, doctors with expertise in several areas meet up to discuss, brainstorm, and share knowledge and experience.

This has been going on for two years. In our latest meeting, it was observed that the number of people testing positive is beyond what was ever seen before. Interestingly, they included even asymptomatic bystanders who had come in to help out with their relatives’ surgery and thus got tested. This shows the amazing spreading power of this variant, quite unlike any previous versions of the SARS-CoV-2 virus.

On the ground, there appears to be widespread infection rates among past infected as well as vaccinated individuals, including those who have received boosters. Thus, this variant has enormous immune escape potential.

Besides, systemic vaccines (given intramuscularly) are not known to elicit adequate mucosal immunity. That said, it is not clear whether mucosal immunity is even possible for the coronavirus, which is a family of viruses that are known for recurrent or repeated infections every few months. Over the past two years, the SARS-CoV-2 virus has been showing the same tendency of its other clan members, that is, recurrent infections even among those who have had prior infection.

As far as the Omicron variant goes, the reasons for its apparent reduction in severity is two-fold. Firstly, unlike Delta, which affected a largely virgin population with very few people vaccinated, Omicron is arriving at a time when a vast majority of adults are already vaccinated, among whom several have had natural infections, in addition.

Thus, it is no longer a novel virus to humanity. This means that our adaptive response system, which is our second arm of immune response, which includes T cells, is able to respond faster. This is because there is long-lasting immune memory.

Studies in the past have shown that those who have suffered severe disease largely did so because of a maladaptive immune response, where adaptive immunity (the second arm) got delayed; and the first arm (innate immune system) response had to compensate by going into overdrive mode. Innate immunity, when stuck in overdrive mode, can cause severe damage to organs. This explains the extensive devastation observed in the first two years of the pandemic.

This second mechanism for a milder disease caused by Omicron is described by a research in Germany by Sandra Ciesek and colleagues, which has shown that Omicron is less adept than Delta in turning off the alarm systems of the cell. In other words, Delta was able to cause a lot more stealth infection compared to Omicron.

As Omicron cannot turn off our natural alarms or interference, our immune system might be able to detect it at an early stage and get rid of it. This information is based on the signals we have at this point in time. Evidence about COVID-19 is rapidly progressing.

Doctors who are involved in the treatment of COVID-19 patients from across the world have consistently said that those who have received two doses of the vaccine have an incredibly low risk of developing severe disease or bad outcomes, compared to the unvaccinated. This aspect of protection has not waned.

What has declined though is the ability of vaccines to stop infections, which was perhaps not very good to start with. I recall the first breakthrough infections being reported from India within a few weeks of the introduction of the vaccine. They were caused by the Alpha variant. They were rare at the outset but more common after around six months.

The May 2021 CDC study on miners in South America who had been double-vaccinated with Pfizer, also showed that it was ineffective in preventing COVID-19 infection. In that series, 60% of vaccinated miners got COVID-19. This was barely five months after vaccines were rolled out. However, across the board, vaccinated people are still less likely to develop infection compared to the unvaccinated. Omicron-specific data for this aspect of protection is not yet available.

What we have also observed is that hospitalisation in the Omicron era is not necessarily a marker of severity of COVID-19. Many people who are admitted to hospitals have a positive diagnosis of COVID-19 simply because they were tested, and not because they are ill from it, which means that they may be admitted to hospitals for treatment of other conditions. Unfortunately, when their number gets counted along with those admitted with COVID-19 pneumonia, the numbers get inflated. Thus, looking forward, hospitalisation is unlikely to remain a reliable indicator for the severity of COVID-19 or while measuring the outcomes of vaccination.

One of the major problems being reported now is manpower shortage at healthcare establishments, government offices, and other enterprises. Decisions on duration of isolation are critical to balance the financial and other losses that occur as a result of time away from work, with the risk involved in bringing somebody back sooner than is safe to do so.

Opinions are divided, but the world is trending towards a five-day isolation period from the date of the onset of symptoms. A study in Japan on Omicron has shown that the most number of viruses in the nose and throat that could be actually isolated were found between day three and six. Beyond Day 10, there was no live virus that could be found.

Doctors have also commented that early during the course of illness, tests are repeatedly showing up negative. It is believed that it might be the result of successful immune elimination of the virus during the early phase. Therefore, testing on day one of symptoms might not be reliable. This might also explain why large symptomatic Omicron outbreaks occurred at social gatherings among vaccinated and boosted people, who had tested negative prior to attending social events. These are early observations and will need to be followed up with systematic studies.

The role of quarantine for international travellers is increasingly being questioned. It was acceptable during the early phase of the epidemic, when the strategy was to contain the virus. However, two years into the pandemic, with such widespread disease, considering the speed of worldwide travel, it is doubtful whether continuing such redundant measures will be of benefit.

There is no doubt that COVID-19 will continue its cyclical tendencies with newer variants. Incidentally, COVID-19 is not the only cyclical virus to infect humans. Many viruses including parvovirus, parainfluenza, influenza, and rotavirus are all known to cause a cyclical pattern, the reasons for which have not been fully elucidated yet.

(As told to G. Krishnakumar)


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Printable version | May 27, 2022 12:42:40 pm | https://www.thehindu.com/news/national/kerala/number-of-covid-19-infected-beyond-what-was-ever-seen-before-health-expert/article38297727.ece