With COVID-19 attaining the level of a pandemic, the question arises, how will it subside and when will the graph begin to drop. In March, the British government was hoping to fight coronavirus off through herd immunity. But what exactly is herd immunity, and will it be a good enough weapon in this war?
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What is herd immunity?
Herd immunity or herd protection occurs when sufficient people are vaccinated, or immunized against a specific disease. According to the Oxford University Vaccine Knowledge Project, herd immunity eliminates the number of vulnerable or susceptible people because the population already has antibodies to fight illness.
For instance, if immunized people have someone with measles in their midst, they will not catch the disease, because their body already possesses the ability to fight this virus. As a result, the disease disappears.
Herd immunity is the basis of all vaccination projects, according to the University of Edinburgh professor of infectious disease epidemiology, Mark Woolhouse. Natural herd immunity can be attained if enough people are exposed to a disease. It does not matter where the immunity comes from vaccination or acquiring the disease. The end result is that an illness or a virus does not attain the status of an epidemic.
Professor Martin Hibberd, of London School of Hygiene & Tropical Medicine, says, that when seventy percent of the population has been infected and recovered, there are fewer chances of reinfections and disease outbreaks.
Herd immunity and COVID-19
By mid-March, the strategy of the United Kingdom was to deal with COVID-19 through building ‘herd immunity’. According to the Chief Scientific Advisor of the UK government, Sir Patrick Vallance, the idea was to allow a sufficient number of people who would have the mild illness to become immune and eventually build herd immunity.
While technically speaking this idea has merit, it cannot be possible to fight coronavirus this way because this is a virus that can cause a high number of hospitalizations and need for critical care. This can put a huge load on the healthcare system and strain the health service capacity past the breaking point.
Simulations of the outbreak showed that hospitals would be overwhelmed if COVID-19 is allowed to run rampant to attain herd immunity. Therefore, after figures from Imperial College London were analyzed, and 501 scientists and mathematicians signed a letter to the UK government, the strategy of fighting coronavirus was changed to social distancing.
Biostatistician, Natalie Dean, at the University of Florida, says the only safe way to attain herd immunity to COVID-19 is through a vaccine. Natalie Dean specializes in infectious disease epidemiology, and according to her we don’t have sufficient data regarding the impact of COVID-19 on different demographics, and therefore, we cannot risk exposing people to the virus for attaining herd immunity.
The calculations for COVID-19 have shown that around 60 to 70 percent of the population needs to be infected for herd immunity to kick in, naturally. On average, one person infected with COVID-19 infects two to three other people, and by reducing the number of people that one virus-laden person infects, the point at which herd immunity is attained can be lowered. The idea is to start herd immunity earlier, at lower numbers, by enforcing social distancing. Ideally, that would be when one infected person only infects one or less than one other person.
Social distancing is the best strategy
From all evidence, at this point in time, social distancing is the key to defeating COVID-19. Protection occurs when the infected people do not come in contact with the uninfected people and transmit the virus to them. This way the chain of transmission is interrupted and the spread of disease is stopped.
COVID-19 is a form of virus i.e. novel, which is why there is a lack of pre-existing immunity, and the whole population is susceptible to infection. The reason why herd immunity cannot sufficiently fight COVID-19 is that viruses are known to mutate and adapt so that they can escape the body’s immune system. An example can be seen in the influenza virus, for which vaccines are updated annually, as every year the virus adapts to form new strains.
There is no information at this point, to know if COVID-19 also mutates a lot and adapts to the new environment. Even if herd immunity is attained, coronavirus can fight the immune system by mutating itself.
The World Health Organization said in its statement that while many people attain immunity to seasonal flu strains, the same cannot be said about COVID-19. So far, this novel virus has shown no trends as to which demographics it affects most. There are also 20 to 40-year-old people lying in the ICU who are affected by this virus. In simpler terms, this virus hasn’t been in the population long enough for the scientists to figure out what it does in immunological terms.
Currently, the WHO reiterates, there is no vaccine to fight COVID-19, and that vaccines against pneumonia do not provide protection against this. Coronavirus is ‘new and different’ and therefore, will need its own vaccine to be effective. Till then, social distancing and hand washing are the ways to go.
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