Herd immunity: In the real world, it''s complicated

(MENAFN - Gulf Times) Even as the Covid-19 pandemic continues to wreak havoc across the world well into a second year, the concept of herd immunity is gradually taking a back seat with vaccination being promoted as the only way out. During the initial months, a number of governments and health authorities appeared to pin their hopes on herd immunity in an approach that would see the virus spread though society and cause infections, but also provoke an immune response in those who have recovered. The theory was that if around 60-70% of the population gained these antibodies then the transmission of the virus would gradually decrease, and those who had not yet been infected would be protected by the increasingly small opportunity the virus had to spread. In reality, Covid-19 swept through the Asia, Europe and the Americas prompting millions of infections — from which millions of people recovered — but also hundreds of thousands of hospitalisations and deaths. To date globally, the virus has caused over 169mn infections and 3.51mn deaths. These numbers are increasing daily. The strategy of targeting herd immunity was quickly abandoned by most countries — with some notable exceptions such as Sweden — and lockdowns became the primary way of trying to prevent the spread of Covid-19 as vaccines were rapidly developed. Now, we have highly effective vaccines and immunisation programmes are continuing apace across the world. This has sparked hope that once enough people in populations have been vaccinated, herd immunity could be achieved — that is, once enough people are vaccinated, the virus will have nowhere to go and will die out. But yet again, Covid-19 is proving to be unpredictable, and we still don’t know how long protection from vaccines, or natural immunity acquired by previous infection, lasts. Vaccine hesitancy in some parts of the world, the role of children below 12 in transmission (as they are ineligible for vaccines) and, most importantly, the emergence of new Covid variants around the world are also unknowns that could also prevent herd immunity, experts warn. Most of them believe Covid-19 will become endemic like the flu (meaning it will continue to circulate in parts of the population, likely as a seasonal threat) while hoping it will become less dangerous over time. Epidemiologist Lauren Ancel Meyers, director of the University of Texas Covid-19 Modeling Consortium, is one of them. According to her, ''even if we don’t achieve full herd immunity, vaccines may help us get to a place where Covid-19 is a significantly less lethal threat.” There has been a lot of misinformation and misunderstanding about the herd immunity threshold, as explained by Meyers. ''Simply speaking, the herd immunity threshold is the fraction of the population that must be immunised before the virus will fade away. But in the real world, it’s complicated. With emerging variants and pockets of low vaccination coverage, there is no guarantee we’ll get there,” she said, noting that it’s important people realise: ''The more people vaccinate, the faster the threat will fade. We may never hit herd immunity on a global stage and fully eradicate the virus. But that doesn’t mean we won’t get back to a sense of normalcy soon. We are already seeing the numbers of new cases and hospitalisations beginning to decline,” Meyers added. So, as of now, vaccination is the only hope in the battle against Covid-19 that has ravaged life like never before.MENAFN30052021000067011011ID1102179706