As the novel coronavirus spreads through most of the world in last few months, the debate over the effectiveness of "herd immunity" continues in global public health policy circles. Herd immunity and vaccination has eradicated disease like smallpox in humans. However, experts say that herd immunity will only be effective on the basis that the virus don't change ways to evade such protective immunity, and also other similar but different corona viruses don't emerge.
Herd immunity, also called community immunity or social immunity is a form of indirect protection from infectious disease that occurs when a large percentage of a population has become immune to an infection. This may occur through either previous infections or vaccination, thus providing a measure of protection for individuals who are not immune. Herd immunity was recognized as a natural occurrence in early 20th century, when it was observed that after a major number of children had become immune to measles, the number of new infections temporarily decreased, including susceptible children. Mass vaccination to induce herd immunity has since become common and proved successful in preventing spread of many infectious diseases. The concept of herd immunity is typically described in the context of a vaccine. When enough people are vaccinated, a pathogen cannot spread easily through the population. Hence, someone infected with a disease if interacts with all others who are vaccinated, transmission will be stopped in its tracks.
Different countries like US, Canada, Spain, UK, Sweden, Taiwan, India, and Italy all have adopted varied approach to tackle Corona condition. Many countries have, or are looking to, promote a controlled spread of COVID-19 in healthy population to achieve herd immunity. Some governments own this strategy, others outwardly dismiss it. Some are aiming at immunity to the coronavirus without a vaccine. Some nations have asked older people and those with basic health issues to self-quarantine but are keeping many schools, restaurants and bars open. But given the fatality rate, there is no way to do this without huge numbers of casualties. Herd immunity can happen by developing resistance to disease through time, but health authorities say the price is too high to take this practice into consideration.
Vaccines and coronavirus herd immunity
There are two ways to produce herd immunity against a disease: develop and administer a safe and effective vaccination, or wait for the disease to make its rounds through a population. The rationale of vaccines is to expose a person to something that induces immunity without making them very sick. Vaccines can be tiny doses of a pathogen or a dead microorganism. Vaccines have been successful in creating herd immunity to several infectious diseases. Lack of vaccination has posed a challenge to herd immunity, allowing preventable diseases to persist in or return to population with inadequate vaccination rates.
Complexity related to herd immunity and the coronavirus spread
Research on COVID-19 is ongoing, and there is no sure treatment available as of now.
There is no widespread resistance to COVID-19, and is still far from developing it. Experts estimate that from 60% to 90% of population must have immunity to a disease to stop spreading. Most countries affected by COVID-19 have not achieved that level including US, which currently has highest number of cases out of all countries.
At this juncture, there’s no enough evidence about effectiveness of antibody-mediated immunity to guarantee the accuracy of a herd immunity or ‘immunity passport’.
Scientists don't know if people can contract the SARS-CoV-2 virus more than once.
It’s not confirmed a positive coronavirus antibody test means immunity from contracting or spreading the virus.
In the beginning, vulnerable group at risk for serious complications was older, fragile, sick people. But later it was realized that even young, healthy people may develop complications leading to fatality, which raises questions about the nature of the virus.
It's impossible to know how many people are affected since not all cases are reported, many remain asymptomatic or don’t get tested, or a test isn’t available.
Experts have raised concerns that immunity passports may intensify economic inequalities, and increase transmission risks by encouraging people desperate for work to try to deliberately infect themselves.
People with positive test result assume immunity to second infection and may ignore public health advice, leading to continued transmission risks. Reports of people including from China and South Korea, who had recovered from the disease testing positive again.
Herd immunity works best when we’ve vaccine and a disease with no serious consequences. With no vaccine for coronavirus, it makes herd immunity less effective, and this disease has serious consequences in some people. It’s not sure when the vaccine under development will become available to the public.
Relying solely on a herd immunity strategy could also be dangerous as it may lower risk perception among younger populations, affecting their compliance with much-needed social distancing measures.
It’s still not clear if a vast majority of the world’s population will inevitably become infected before a vaccine becomes available. However, due to seriousness of COVID-19, most experts argue that without a vaccine, it may do more harm. World Health Organization(WHO) is reviewing evidence on antibody responses to the virus. Most studies have shown that people recovered from infection have antibodies to the virus, but it’s unclear if they provide protection. A vaccine may take a minimum of 12-18 months; this time frame carries risks and there is no guarantee. Without an effective vaccine, community immunity is the only option to protect the vulnerable and end this pandemic.
As per WHO the pandemic will end when we achieve herd immunity, which will be either natural through acquiring the infection or artificial through vaccine induced immunity. It is really an intriguing race between Mother Nature and the science as to who will succeed in protecting the herd (Population) first. Until then, Be safe and protect yourself and others.
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