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Researchers who designed a transmission model for COVID-19 showed that attempting to establish herd immunity against COVID-19 would be too challenging.
New research suggests that achieving herd immunity to COVID-19 is an impractical public health strategy. The researchers suggest that the idea of ’mitigating’ the COVID-19 disruption by achieving herd immunity would require constant changes in lockdown measures, making it too difficult to achieve.
The study was based on a new model developed by scientists at the University of Georgia, USA, who said that the top two schools of thought when it comes to preventing healthcare infrastructure from being overwhelmed, while avoiding Important social disorders are:
- repression, in which communities implement drastic social distancing measures to eliminate transmission; and
- mitigation, a strategy that aims to achieve herd immunity by allowing the infection of a sufficiently large proportion of the population without exceeding the capacity for health care.
“The concept of herd immunity is tempting because it spells the end of the COVID-19 threat,” said Toby Brett, postdoctoral associate at the Center for Infectious Disease Ecology at the University of Georgia, USA, and lead author. of the study. “However, because this approach is aimed at preventing disease elimination, a constant adjustment of lockdown measures would be necessary to ensure that there are enough, but not too many, infected at any given time. Because of these challenges, the herd immunity strategy is actually more like trying to walk a barely visible tightrope. “
In their study, Brett and Pejman Rohani developed a model to investigate suppression and mitigation approaches to control the spread of SARS-CoV-2, the virus that causes COVID-19. Unlike other similar studies, Brett and Rohani sought to determine whether and how countries could achieve herd immunity without overwhelming the health care system, and to define the control efforts that would be necessary to do so.
Their age-stratified disease transmission model simulated SARS-CoV-2 transmission in the UK, with spread controlled by self-isolation of symptomatic individuals and various levels of social distancing.
In their simulations, the pair observed that in the absence of control measures, the UK would experience up to 410,000 COVID-19-related deaths, of which 350,000 would be in people aged 60 and over. They showed that using the suppression strategy, far fewer deaths were predicted: 62,000 among people <60 years and 43,000 among people under 60 years.
Their model also indicated that if participation in self-isolation is high (defined as a reduction of at least 70 percent in transmission), suppression could be achieved in two months regardless of social distancing measures and potentially sooner if the school , work and social gathering places should close.
Examining strategies that seek to develop herd immunity through mitigation, their model found that if social distancing is kept at a fixed level, hospital capacity should greatly increase to prevent the healthcare system from becoming overloaded. To achieve herd immunity with currently available hospital resources, the UK should adjust social distancing levels in real time to ensure that the number of sick people is equal to, but not greater than, the hospital’s capacity. If the virus spread too fast, hospitals would be overwhelmed, but if it spread too slowly, the epidemic would be suppressed without achieving herd immunity.
Brett and Rohani noted that much is unknown about the nature, duration, and efficacy of COVID-19 immunity and that their model assumes perfect and long-lasting immunity. They cautioned that if immunity is not long-lasting and there is a significant possibility of reinfection, it is highly unlikely to achieve herd immunity through widespread exposure.
“We recognize that we have a lot to learn about COVID-19 transmission and immunity, but we believe such a model can be invaluable in so-called ‘situation analyzes,'” said Rohani. “The models allow stakeholders to think about the consequences of alternative courses of action.”
The study was published in PNAS.
