Aiming to achieve herd immunity to coronavirus is an impractical strategy, says a new study published in the journal Proceedings of the National Academy of Sciences .

Researchers said that immunity can be unpredictable and achieving it through widespread exposure is unlikely. The researchers studied the suppression and mitigation approaches to curb the transmission of the novel coronavirus. They wanted to explore if and how countries could achieve herd immunity without depending on the health care systems.

Study lead author Toby Brett from the University of Georgia in the US said: “The herd immunity concept is tantalising because it spells the end of the threat of Covid-19.” Brett added: “However, because this approach aims to avoid disease elimination, it would need a constant adjustment of lockdown measures to ensure enough people are being infected at a particular point in time.”

According to their thesis, in the absence of any control measures, the United Kingdom would experience as many as 4,10,000 deaths related to Covid-19, with 3,50,000 deaths related to people of age 60 and above. They found if the government implements restrictions and places an effective suppression strategy, the mortality rate can be brought down to 62,000 among individuals aged 60-plus and 43,000 among individuals under 60.

If self-isolation engagement is high (defined as at least 70 per cent reduction in transmission), suppression can be achieved in two months regardless of social distancing measures, and potentially sooner should school, work and social gathering places close, researchers added. They noted that instead of focusing on achieving herd immunity, the UK should implement strict social distancing protocols and ensure that the number of sick people is equal to, but not beyond, hospital capacity.

The team wrote in their study: “If the virus spreads too quickly, hospitals will be overwhelmed, but if it spreads too slowly, the epidemic will be suppressed without achieving herd immunity.” They further stated that much is unknown about the nature, duration, and effectiveness of Covid-19 immunity and that they assumed perfect long-lasting immunity for their study.

The team further cautioned that if immunity is not perfect, achieving herd immunity through widespread exposure becomes more unlikely and impractical. “We recognise there remains much for us to learn about Covid-19 transmission and immunity,” said study authors.

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