NEW DELHI: The measles virus is a champion spreader. One person with measles can infect 12-18 others. On average, one coronavirus patient infects fewer than three. Both measles and Covid spread through the air, so why don’t we wear masks to keep measles at bay?
There are two reasons. The measles vaccine (MMR) is extremely effective. After two doses, you have 97% protection, which is equal to the best of Covid vaccines. More important: Everyone around you is vaccinated for measles. Chances of running into it are dim.
Does that mean we won’t need to wear masks when most people are vaccinated for Covid? In the US, for example, the Centers for Disease Control and Prevention (CDC) now says, “Anyone who is fully vaccinated can participate in indoor and outdoor activities, large or small, without wearing a mask or physical distancing.”
US President Joe Biden’s chief medical adviser Dr Anthony Fauci is more cautious. He says fully vaccinated Americans don’t need to wear masks outdoors unless “people are essentially falling over each other.”
In the US, 45% of adults are fully vaccinated while about 60% have got at least one dose. It’s aiming for 70% coverage by July 4. Also, most Americans have taken mRNA vaccines with efficacy scores of 95%.
The picture in India looks very different. Roughly 15% of the adult population (95 crore) has got at least one dose, and 4% both doses. Of the entire 130-crore population, just 3% is fully vaccinated.
Our vaccines, Covishield and Covaxin, have lower efficacy rates of about 80%. We are also grappling with new variants at the peak of a deadly second wave. So, going maskless could be risky even for the fully vaccinated in India.
As AIIMS director Dr Randeep Guleria said recently, “This virus is very clever and keeps mutating, we cannot say what will be the protection from vaccines as far as new emerging variants are concerned.” But masks and distancing work against all variants, he added.
Lesson from Seychelles
A vaccine’s efficacy score shows how well it protects you from falling ill. While all vaccines are good at preventing severe disease, the best ones also ward off the milder sym ptoms better. The Seychelles is learning this the hard way.
By April, it was the “world’s most vaccinated country.” More than 60% of its 1 lakh population had got two doses. Yet, the first week of May left it grappling with a big outbreak. A Washington Post report says the country’s main treatment centre filled up, and doctors and nurses also fell ill.
While most new patients in the Seychelles had not been vaccinated, 35% had got both shots – and there’s a lesson for India in this. Like India, the Seychelles uses two vaccines. About 40% doses are of made-in-India Covishield, and the rest are madein-China Sinopharm shots.
The Sinopharm vaccine is an “inactivated vaccine with an adjuvant” – similar to India’s Covaxin. WHO says it has 78% efficacy against symptomatic infection.
If the Seychelles could have an outbreak after 60% coverage with these vaccines, India should not let its guard down. There, the population-wide immunity was estimated at less than 50% (60% population, multiplied by 80% efficacy). In India, it would be just over 2% (3% population, multiplied by 80% efficacy).
Risk from new variants
A new virus variant called B.1.617 and its offshoots are suspected to have fuelled India’s second wave. B.1.617 has spread to over 40 countries, and in the UK, cases caused by one of these offshoots – B.1.617.2 – doubled in a week. On May 11, B.1.617.2 became only the fourth global ‘variant of concern’. Germany is so worried about its spread that it has put Britain on a list of “risk areas.”
It’s still not clear if the B.1.617 virus family is more dangerous but UK scientists are confident B.1.617.2 is a fast spreader and will “eventually ‘dominate’ cases in the UK,” a BBC report says. By one estimate, it could spread 50% faster than the current reigning variant.
The Economist mentions 15 cases of B.1.617.2 in a London care-home among people who had taken both doses of the AstraZeneca (Covishield) vaccine. The good news is, the vaccine worked well and nobody died.
So yes, vaccination will protect you from severe disease, but if you catch the virus you could pass it on to someone who is not vaccinated. That’s why, for your own sake and for others, continue wearing a mask after vaccination.