Many factors contribute to community-building COVID herd immunity. Are we close to having herd immunity against Covid-19? Can we achieve that? Let’s find the answer.
What do you think can we achieve COVID herd immunity?
As people are still getting used to life with less restrictions in many areas of the world, everyone has begun to wonder when the pandemic will end. With new variants showing up every few months and wreaking havoc, the possibility of gaining COVID herd immunity decreases with each passing day.
The herd immunity threshold can be achieved with high vaccination rates, which is why some experts believe that once 60% to 70% of people get vaccinated, society would be able to return to normal. This immunity can be due to vaccinations or past exposure to the virus.
This belief has started to shift as the pandemic is nearing its second year. Youyang Gu, an independent data scientist, changed his Covid-19 forecasting model from “Path to Herd Immunity” to “Path to Normality”. According to him, due to the hesitancy to get vaccinated and the arrival of new variants, reaching COVID herd immunity is looking impossible.
As per Lauren Ancel Meyers, epidemiologist and executive director of the University of Texas at Austin COVID-19 Modeling Consortium, “We’re moving away from the idea that we’ll hit the herd-immunity threshold and then the pandemic will go away for good.”
The shift from looking forward to COVID herd immunity to it looking less likely does not change the fact that vaccinations are helping us gain protection against Covid-19. In the long-term, Covid-19 is likely to become an endemic disease, just like the Spanish flu in the past. However, in the near future, scientists believe that the new normal may not include herd immunity anymore.
What is COVID Herd Immunity?
Herd immunity occurs when a vast majority of a community gains immunity against a disease, which makes it unlikely for the disease to spread from person to person. The COVID herd immunity ensures that the community as a whole becomes immune to the disease.
For the disease to spread in a community, a particular percentage of the population has to be capable of getting the disease. The spread of the disease will decrease when a more significant portion of the population is immune to the disease compared to the people capable of contracting it.
With diseases that are more contagious, the percentage of the population that is immune has to be incredibly high. For example, measles is an extremely contagious disease, and the estimate is that 94% of any community has to be immune to measles to stop the chain of transmission.
How Can Herd Immunity Be Achieved?
1. Vaccines
One of the most efficient ways of gaining COVID herd immunity is through vaccinations. Through vaccinations, enough people can develop antibodies against disease and gain protection against future infections.
The vaccination method is different from the natural infection method as it does not result in health complications or illness. Vaccines have helped develop herd immunity against various diseases in the past like rubella, smallpox, polio, diphtheria and more.
With the help of COVID herd immunity, people who are immunocompromised and newborns can be protected against the disease even if they cannot get vaccinated. However, the uneven rollout of vaccines all over the world and hesitancy to get vaccinated can cause hindrance in gaining herd immunity through Covid-19 vaccines.
2. Natural Infection
Herd immunity through natural infection is achieved when a large majority of the population contracts the disease and recovers from it. This infection leads to antibodies being formed in our bodies that can help us gain protection against the disease.
However, gaining herd immunity against Covid-19 through natural infection is not risk-free and safe. There are always factors that can have an effect on COVID herd immunity. With natural infection, there is a risk of reinfection. There have been cases where people have contracted Covid-19 after recovering from it earlier and having antibodies.
According to experts, 70% of the population in the U.S. would have to recover from Covid-19 in order to establish herd immunity and halt the spread. 70% of the U.S. population means more than 200 million people. When such a significant portion of the population suffers from Covid-19, there are bound to be millions of health complications and deaths. The risk is far too substantial to develop herd immunity through natural infection.
Why Does Herd Immunity Against Covid-19 Look Less Likely?
Uneven Vaccine Roll-Out
According to Matt Ferrari, an epidemiologist at Pennsylvania State University’s Center for Infectious Disease Dynamics in University Park, the distribution and speed of rolling out vaccines matters for multiple reasons.
A coordinated effort to distribute vaccines all over the country could have helped wipe out Covid-19. However, there are various disparities in distributions of vaccines everywhere in the world, which makes it close to impossible for us to reach COVID herd immunity through vaccination.
Access to vaccines all across the U.S. has been incredibly uneven. States like New Mexico and Alaska have 16% of their population fully vaccinated, whereas 10% of the population of Utah and Georgia is fully vaccinated. The disparities are not just between countries, but also within the countries.
The distribution of vaccines in most countries is decided based on age. People who are older and at more risk of suffering from Covid-19 are prioritized when giving vaccinations. With vaccines getting approved for children, there are more people in the country who can be vaccinated to help facilitate the herd immunity threshold.
The vaccine rollout is also affected by geographical factors. Communities cannot be islands, especially in the United States. There have been instances where a variant of Covid-19 has spread across the country due to one community being infected. When developing COVID herd immunity, it is challenging to keep one group of people isolated in a geographical location. We have to think of the entire country as a whole.
Due to geographical clustering, the path to COVID herd immunity becomes more and more convoluted. It is not a straight line like experts previously thought it would be. If one community develops herd immunity but the surrounding communities don’t, mixing with each other will only lead to more Covid-19 outbreaks.
It Is Uncertain Whether Vaccines Prevent Transmission
The critical factor of COVID herd immunity is even if one person is infected with Covid-19, they should not have susceptible hosts around them to maintain the chain of transmission. If there are people around that are not immune to the virus, the disease will continue to affect the population.
Covid-19 vaccines like Pfizer and Moderna have been successful in building some immunity against the disease and preventing symptomatic disease. Still, there is no conclusive evidence that these vaccines also stop the transmission of Covid-19. This uncertainty is a significant problem when it comes to establishing herd immunity.
According to Shweta Bansal, a mathematical biologist at Georgetown University in Washington DC, “Herd immunity is only relevant if we have a transmission-blocking vaccine. If we don’t, then the only way to get herd immunity in the population is to give everyone the vaccine.”
The effectiveness of vaccines that stop transmission has to be significantly high in order to maintain herd immunity. This effectiveness does not have to be 100% for herd immunity to increase. In fact, if they have an effectiveness of 70%, it is enough for a community to gain COVID herd immunity. However, even with vaccines that halt transmission, it is an uphill battle to break transmission chains.
Consequences Of New Variants
After every few months, there are new Covid-19 variants that sprout up across the world and spread everywhere. These new variants are often more transmissible and can be resistant to vaccines. We are at a stage where we are racing against the new variants. The more time it takes to stop the transmission of Covid-19, the more time new variants have to develop and spread across the globe.
The city of Manaus in Brazil is an example of how new variants can have harmful effects on building herd immunity. The city was hit severely by Covid-19 during May and October of last year. Experts believe that 60% of the population had been infected with coronavirus by June 2020, and this percentage should have been enough to meet the COVID herd immunity threshold.
However, in January of 2021, there was a massive resurgence of Covid-19 cases in Manaus. This rise in the cases was due to the emergence of a new Covid-19 variant, P.1. The effect of the P.1 variant proved that the earlier infections did not provide complete immunity from future diseases. The resurgence even after the city had a high level of immunity shows that new variants can have various consequences on the COVID herd immunity of a community.
Quick and thorough vaccinations might be the only way to halt the transmission of new variants. However, the uneven roll-out of vaccines all over the world is a massive hurdle. Currently, we are stuck in a place where there are similar levels of disease and immunity.
Developing vaccines also gives way to other pressures. For example, vaccines that stop transmission can provide the virus with a chance to evolve into more transmissible variants.
Vaccines Change Human Behavior
As more people get vaccinated, they change the way they interact with others around them. People all over the world started going out and meeting people more freely after getting inoculated. This increase in interactions changes the COVID herd immunity equation. More people are exposed to the virus if the restrictions are eased.
The vaccines are not bulletproof and do not provide people with 100% protection and prevention. If you were meeting one person before getting vaccinated and ten people after getting vaccinated, you are putting more people at risk.
Many people in the world have been waiting for life to go back to pre-pandemic times. After getting vaccinated, even governments have started lifting mask mandates and social distancing regulations. Although only 59% of people in the United States have been fully vaccinated, many people have stopped following the safety rules altogether.
Final Takeaway
Covid-19 has spread all over the world and caused lots of setbacks. When the pandemic first started, experts believed that we would be able to develop COVID herd immunity with the help of vaccines and natural infection.
However, that is looking less likely as new variants appear, and the distribution of vaccines is not adequate. We are living in uncertain times where we don’t know how effective vaccines are at stopping transmission, and human behavior changes with an increased rate of vaccination.
