Kerala

Need to curb silent transmission to rein in COVID

People wait to receive a dose of COVID-19 vaccine at the Government Homoeopathic Medical College Hospital in Iranimuttom, Thiruvananthapuram, on Saturday.   | Photo Credit: S. GOPAKUMAR

People with no symptoms transmit more than half of all cases of the novel coronavirus (because they are mobile), according to a recent model developed by the U.S. Centers for Disease Control and Prevention.

This essentially means that having a grip on silent transmission from persons without symptoms is very important for controlling the pandemic.

The question of asymptomatic transmission post-vaccination is now being explored by the U.S. National Institute of Allergy and Infectious Diseases. Last month, Anthony Fauci, U.S. President’s chief medical advisor and director of NIAID, announced a new trial, PreventCOVIDU, which will study if vaccines prevent disease transmission post-vaccination.

Dr. Fauci said during the announcement that while it is well-established that vaccines are effective in preventing symptomatic illness, the prevailing question is, if individuals get infected and are asymptomatic, do they transmit it to their close contacts?

Israeli findings

Nature Medicine reported in March that Israeli researchers had found that vaccinated people who contracted COVID had lower viral loads than people not vaccinated who got infected.

However, while a lower viral load suggested less infectiousness, there is no current information on what constitutes an “infectious dose” of SARS-CoV2 for people

Surprisingly, the State’s Health department seems to totally discount the contribution of asymptomatic cases to disease transmission.

State guidelines

The guidelines framed by the department for augmented testing on April 15, says that persons who recovered from COVID in the last three months and those who have received two doses of vaccine may be excluded from RT-PCR testing if they have no symptoms.

“If we are totally excluding asymptomatic people from testing, how are we going to gather data on breakthrough infections? From a public health perspective, it is important to explore the impact of asymptomatic infections in fully vaccinated people on disease transmission. It might even give us more insights into the second wave,” a public health expert said.

What is crucial now is how well the State is documenting and following up these cases of breakthrough infections and reinfections and if there has been any onward transmission from them amongst family or friends. Most importantly, genome sequencing should be done in every one of these cases and any cases of onward transmission among family and friends, to check if mutant variants are being disseminated.

It is also essential that effective containment measures are initiated right now to keep keep infection levels low so that there's less selection pressure on the virus to evolve into newer variants.

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Printable version | May 7, 2021 5:18:59 PM | https://www.thehindu.com/news/national/kerala/need-to-curb-silent-transmission-to-rein-in-covid/article34394484.ece

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