Almost no one was immune when the coronavirus (COVID-19) first began to spread. The virus spread rapidly through populations because of the lack of resistance to it. As for now, vaccinations for COVID-19 are available in all countries, so why is it important for everyone to take it? This leads to ‘herd immunity’, that can act as a shield to protect those who aren’t/ cannot take vaccines (like children).
When the majority of a population is resistant to an infectious disease, it offers an indirect protection to those who aren’t immune to that particular disease. This is known as population immunity/herd immunity (also known as herd protection).
For instance, if 80% of a population is resistant to a virus, four out of every five people who come into contact with someone who has the disease will not become ill (and therefore will not transmit the disease). In this way, infection transmission can be slowed and can keep under control. Until infection rates begin to decrease, 50 percent to 90 percent of a population must have immunity, depending on how infectious an infection is. But, particularly in the case of a novel virus, this percentage cannot be kept as an indicator that must be crossed. This number will rise or fall depending on viral evolution and changes in how people communicate with one another. Immunity in the population (for example, from vaccination) may still have a beneficial impact below any “herd immunity threshold.” Infections will still happen above the threshold.
The greater the gain, the higher the degree of immunity. This is the importance of getting everyone vaccinated.
Few methods that have been used in other infectious disease spread to gain herd immunity
Polio, mumps, measles, and chickenpox are examples of infectious diseases that were once widespread but are now uncommon because of vaccines. We occasionally see outbreaks of vaccine-preventable diseases in populations with poor vaccination coverage (like in rural areas) due to a lack of herd immunity.
Even if many adults have gained immunity as a result of prior infection, infections without a vaccine can still spread among children and infect those with compromised immune systems. This was observed for many of the diseases listed above prior to the development of vaccines.
In the case of infectious disease like chickenpox, the person once infected develops immunity towards it which helps him from getting infected for the second time. But infections getting settled without a vaccine can be a trouble for the other people coming in contact with him. He may not get infected for the second time, but can transmit it to others.
Few other viruses (such as the flu) mutate (changes/evolves) over time, antibodies from past infections only provide protection for a limited time. This is less than a year in the case of flu. If SARS-CoV-2, the virus that causes COVID-19, is like other coronaviruses currently infecting humans, infected people should be immune for months to years. In Denmark, for example, population-based studies have shown that an initial SARS-CoV-2 infection protects against reinfection for more than six months. However, individuals with weakened immune systems (such as the elderly) may have lower levels of immunity, and it is unlikely to last a lifetime. This is why SARS-CoV-2 vaccines are also needed.
How can we achieve herd immunity with SARS-CoV-2?
Herd immunity can be achieved in two ways, much like every other infection: A significant portion of the population is affected or receives a preventive vaccine. According to what we know so far about coronavirus, if we really want to return to a pre-pandemic lifestyle, we’d need at least 70% of the population to achieve herd immunity to keep infection rates low without putting strict restrictions on behaviours. However, several factors influence this degree, including the virus’s infectiousness (more infectious variants will evolve) and how people communicate/come-in contact with one another.
Infection rates slow down as people minimise their level of contact (by following COVID-19 protocols like distancing themselves, wearing masks, etc.). Infection rates will rise again as culture becomes more accessible and the virus mutates to become more infectious. We are not yet sure at what level of safety will enable life to return to normal without another hike in cases & deaths.
What are the different ways herd immunity could manifest?
The best way is to vaccinate people as soon as possible while preserving distance and other infection-prevention steps. This will necessitate a concerted effort on the part of everyone. However, if we manage to vaccinate the population at the current pace, we should see significant reductions in transmission 2021. Although there will be no “herd immunity day” when life returns to normal, this strategy gives us the best long-term chance of surviving the pandemic.
The most probable result would be somewhere in between these two extremes. Infection rates will likely be unstable (rise & fall) during the spring and early summer (or longer if attempts to vaccinate the population stall). We can loosen distancing measures when infection rates decline, but this may lead to a rebound in infections when people communicate more closely. We will then need to re-implement these steps in order to reduce infection rates.
Would herd immunity ever be achieved?
Yes, but it necessitates universal vaccination of all segments of the population, including people of all ages and races, in all cities, suburbs, and rural areas. Since people are so intertwined, an outbreak anywhere can lead to a revival anywhere. This is a worldwide problem as well. SARS-CoV-2 will start to perpetuate and mutate as long as there are unvaccinated populations in the world, and new variants will arise. Booster vaccination may be required in the United States and elsewhere if variants emerge that can evade the immune response elicited by current vaccines.
Until widespread vaccination, a sustained effort will be needed to prevent major outbreaks. Even then, SARS-CoV-2 is unlikely to be eradicated; it will most likely infect children and others who have not been vaccinated, and we will almost certainly need to update the vaccine and administer booster doses on a regular basis. However, the current waves of explosive spread are likely to fade away in the future, as enough of the population would be immune to provide herd defence.
What can we expect in the coming months?
Before various unpredictable factors take turns on us like the mutation of the virus, the climate change, even our own reactions to government protocols for controlling the pandemic, it is better to get vaccinated as soon as possible. Like we already said before, the more people getting vaccinated, the safer it is for everyone.
But we know this is not an easy task, to get everyone vaccinated in a blink of an eye. It takes time! What is possible to do is, you can take care of your health by taking proper precautions and boosting your own immunity. For that, we must ensure we eat healthy foods that contain elements to boost our immunity system. Limit the spread of the virus by wearing masks, keeping a safe distance and avoiding gatherings. Get vaccinated, gradually immunity will develop within us to resist this virus and everything gets back to a “normal” situation.
Check out – ‘Combat COVID-19 with your immunity’