Most experts and the World Health Organisation estimate that global herd immunity is unlikely to be achieved this year.
Like everything else, the pandemic has also become politicised, with some politicians having claimed that the best cure for the virus was herd immunity.
Herd immunity refers to the development of a collective capability of resistance against a specific disease.
Early on during the pandemic, both British Prime Minister Boris Johnson and former US President Donald Trump trusted herd immunity, and downplayed lockdowns and public preventive measures before they themselves ended up hospitalised with Covid-19.
Despite political hurdles, many medical experts and the World Health Organisation (WHO) have remained cautious, believing that global herd immunity might not arrive this year on the grounds that the virus continues to mutate across the world, creating new life-threatening variants.
"We are not going to achieve any levels of population immunity or herd immunity in 2021," said Soumya Swaminathan, the WHO’s chief scientist, during a briefing last month, despite finding that researchers made “incredible progress” to develop several vaccines.
"We won't get back to normal quickly. We know we need to get to herd immunity and we need that in a majority of countries, so we are not going to see that in 2021," said Dale Fisher, chairman of the WHO's Outbreak Alert and Response Network, during a press conference in January.
"There might be some countries that might achieve it but even then that will not create 'normal,' especially in terms of border controls," Fisher noted.
While some countries like the US might arguably get closer to the point of herd immunity, the story could be completely different for countries like India.
India is home to the world’s second largest population, with millions live in densely populated cities, and is much further away from that point, according to both experts and officials.
Experts like Christopher Murray, the director of the Institute for Health Metrics and Evaluation (IHME) at University of Washington, thinks that global herd immunity will not be reached anytime soon, despite 95 percent effectiveness of new vaccines like Pfizer and Moderna.
“Some political and public health leaders have argued that if we vaccinate 70 percent or 80 percent of the global population we can effectively end further transmission,” Murray wrote.
“But even countries fortunate enough to procure sufficient quantities of vaccine may never reach herd immunity, in which case Covid-19 could become a seasonal affliction that comes each year,” he maintained.
Murray sees a distant possibility that the global community might reach herd immunity by next winter. But even that possibility is “increasingly unlikely" according to Murray.
“Because COVID-19 is seasonal, the level of immunity necessary to stop transmission in the summer will be much lower than the level of immunity required in the winter. Because different populations have different baseline frequencies of social interaction, we should also expect levels of herd immunity will vary by community,” Murray observed.
He adds that the scarcity of vaccine supplies, particularly when it comes to various undeveloped countries across the world, is another crucial factor that might prevent us from achieving global herd immunity.
The US might reach herd immunity soon
But the situation is different in the US, where the virus has been deadliest compared to other countries, according to Murray and other experts.
“The United States has considerable vaccine purchase agreements, in addition to its population's cumulative exposure to the virus over the last year, and may reasonably expect to reach herd immunity in the summer months — but may still fall short of a winter-level of herd immunity,” the professor said.
Despite heavy politicisation of the issue in the US, some American experts expect herd immunity to be achieved much earlier than Murray does.
“Amid the dire Covid warnings, one crucial fact has been largely ignored: Cases are down 77% over the past six weeks. If a medication slashed cases by 77%, we’d call it a miracle pill. Why is the number of cases plummeting much faster than experts predicted?” wrote Marty Makary, a professor at the Johns Hopkins School of Medicine and Bloomberg School of Public Health.
Makary believes that cases in the US are down due to the natural immunity the country has acquired after much of the population has been exposed to the virus, killing nearly 500,000 people with millions of cases. The professor estimates that by April, Covid-19 will largely have dissipated.
“Many experts, along with politicians and journalists, are afraid to talk about herd immunity. The term has political overtones because some suggested the U.S. simply let Covid rip to achieve herd immunity. That was a reckless idea,” Makary maintained.
“But herd immunity is the inevitable result of viral spread and vaccination. When the chain of virus transmission has been broken in multiple places, it’s harder for it to spread—and that includes the new strains,” he added.
The professor also drew attention to the fact that other countries like the UK, South Africa and Brazil, which have seen the emergence of new variants, also recorded “significant declines” in their daily new cases.
Makary also disclosed that at least half of his colleagues believe what he says about American herd immunity, while aren't outspoken like he is.
“Some medical experts privately agreed with my prediction that there may be very little Covid-19 by April but suggested that I not to talk publicly about herd immunity because people might become complacent and fail to take precautions or might decline the vaccine,” he said.
“But scientists shouldn’t try to manipulate the public by hiding the truth,” he added.