Saturday, Aug 01, 2020 14:15 [IST]
Last Update: Saturday, Aug 01, 2020 08:32 [IST]
There have been a lot of discussions across the global on “herd immunity” in our fight against this current pandemic. Meeting no resistance, the Covid-2019 virus spread quickly across communities. Stopping it will require a significant percentage of people to be immune. But how can we get to that point? This is where herd immunity could play a role.
So what exactly is herd immunity? When most of a population is immune to an infectious disease, this provides indirect protection—or herd immunity (also called herd protection)—to those who are not immune to the disease.
For example, if 80% of a population is immune to a virus, four out of every five people who encounter someone with the disease won’t get sick (and won’t spread the disease any further). In this way, the spread of infectious diseases is kept under control. Depending how contagious an infection is, usually 70% to 90% of a population needs immunity to achieve herd immunity.
As with any other infection, there are two ways to achieve herd immunity: A large proportion of the population either gets infected or gets a protective vaccine. Based on early estimates of this virus’s infectiousness, we will likely need at least 70% of the population to be immune to have herd protection.
Will this strategy work for India? Union Health Secretary Rajesh Bhushan does not think so. On Thursday he seemed to rule out herd immunity as a strategic option in our battle against Covid-2019. Speaking at the daily Health Ministry briefing on July 30, Bhushan was categorically stated that India’s large population meant an outcome like that would come at a “very high cost.” “No, it is not (a strategic option), in a country like India, with a population of roughly 138 crore (people), it can only be an outcome, at a very high cost,” he said. Bhushan further explained that since herd immunity relied on indirect protection from infectious diseases such as Covid-19, the same would only be possible when a large number of the population becomes immune or once vaccination is complete. He instead advised “sustained Covid-19 appropriate behaviours” to combat the spread. Bhushan also spoke about the progress of two indigenous vaccines, stating that they are under Phase 1 and 2 clinical trials. Testing for these is being conducted with over 1,000 subjects each.
This may actually be a valid argument at this point of time. Recent sero-surveys conducted in cities such as Delhi and Mumbai found high levels of exposure to the virus, giving rise to talk that we would all be better off exposing ourselves to the virus to develop antibodies. Once enough of us had internal defences, it was said, our chain of infections would snap. India’s low fatality rate was cited in favour of the idea. But it had to be rejected.
For one, India’s population is too vast and spread out. Two, a quest for herd immunity would endanger the elderly and other vulnerable groups. Moreover, we don’t know how long the natural immunity gained through casual contact lasts. Some studies suggest that such antibodies lose efficacy within months. Yet, it’s true that every Indian needs immunity. The best way to deliver this, though, would be through mass vaccination once a vaccine passes safety tests and is ready for use. We need a government-funded programme that covers every citizen. Even if this costs a lot, free shots should be made available to all.