India's official COVID-19 tally on Wednesday was 4,18,480 (4.18 lakh), the third highest in the world after the US and Brazil.

'We know that there are new variants which are more transmissible. We know that human behaviour determines the spread of this virus. Therefore, it is not very relevant if we declare whether the second wave is over or not'

Though there is enough anecdotal evidence of COVID-19 catching children -- early teens and younger -- there is little reason to panic, said several doctors and scientists. They also stressed on the urgent need to vaccinate children to stem the spread of the infection.

Those who have recovered from COVID-19 respond faster to the Covishield vaccine and reach high antibody levels, says a study, leading to hopes that they may not need a second dose and therefore help widen India's corona immunisation cover.

While there is a glimmer of hope and India's COVID-19 numbers are on a definite decline for a combination of reasons, a vaccination programme continues to be important, particularly given the presence of a mutant, more transmissible strain, several experts said while cautioning against infection upticks ahead.

Over time, as more mutations occur, the vaccine may need to be altered.

India has purchased 500 million doses of the Oxford University-AstraZeneca vaccine candidate, one billion from the United States company Novavax and 100 million doses of the Sputnik V candidate from Russia's Gamaleya Research Institute, according to the US-based Duke University Global Health Innovation Center.

There are worrying signs that the resolve to continue adhering to the dos and don'ts of the times -- physical distancing, wearing masks and maintaining hygiene protocol - is flagging. This recklessness, more evident ahead of Diwali, may lead to a resurgence in novel coronavirus infections and stall the progress in curbing the disease, the experts said.

Long-term exposure to chronically high PM2.5 levels weakens the ability of the lungs to fend off infections, therefore making people more susceptible to COVID-19, the scientists said.

Some vaccine frontrunners are in advanced stages of trial and could hit the market by early next year, making the task of securing "last mile connectivity" and ensuring that nothing goes wrong before the shot is administered more urgent.

Named after Satyajit Ray's famed detective, the Feluda test, which is priced at Rs 500 and can deliver a result in 45 minutes, is able to differentiate SARS-CoV-2 from other coronaviruses even if genetic variations between them are minute.

The expert noted that in India the pandemic is unlikely to be over in the months to come, and the number of people getting infected will continue to rise.

'There are not enough RT-PCR tests and they take a long time to do in specialised centres. So the world is using RA tests for the same reason that India is using them, and with similar somewhat spuriously comforting rationale'

As worries over India's COVID-19 spike mount -- the country added 75,809 cases on Tuesday to take its tally to 42,80,422 -- scientists are grappling with the pivotal issue of antibodies and trying to understand how they impact on the progression of the disease.

The researchers, including those from the Centre for DNA Fingerprinting and Diagnostics (CDFD) in Hyderabad, advise testing asymptomatic primary and secondary contacts followed by surveillance.

Scientists around the world, including in India, suggest it hasn't been tested properly given the time constraint and there may not be enough evidence to prove its efficacy.

The impact of a 'dengue-COVID-19' season would entail two different diagnostic tests and extract a huge toll on patients too, each disease making the other more complicated to deal with and perhaps more fatal.

'We must not compromise with the standard, the quality. We don't need to be the first to launch a drug but what we need is a Made in India vaccine that the entire world can rely on'

According to the World Health Organisation, 10 candidate vaccines for COVID-19 are in the clinical evaluation and 126 are in the pre-clinical stage.

Early data from its vaccine candidate 'mRNA-1273' showed it produced protective antibodies in a group of eight healthy volunteers, Moderna said. The other closely watched COVID-19 vaccine is the one being developed by scientists at Oxford University.