by Health Desk | Published on September 15, 2022 – Updated on September 15, 2022 | Explainer

Summary: A “wall of immunity” or “immunity wall” is a broad term used to describe how well-protected a group of people are likely to be against a virus – in this case, the virus that causes COVID-19. An immunity wall isn’t a set amount of protection against COVID-19 that a population has, it’s a term that ecompasses all levels of population protection against COVID-19, even if that level of protection is low.

What our experts say

As the COVID-19 pandemic continues on, experts are working to both determine 1) how protected different populations are against the current virus variant(s) circulating, and 2) how to increase the level of protection across populations against the current virus variants and potential future ones.

One way to describe this level of protection is the term “immunity wall,” or “wall of immunity.” This is a crude, broad term to describe how well-protected a group of people are likely to be against a virus – in this case, the virus that causes COVID-19.

The term is primarily used when discussing vaccination, because of how much vaccination levels play a role in how much immunity (protection) a person and a population has to protect them against COVID-19. The higher the vaccination rate, the higher the “wall” of immunity there is.

However, vaccination is not the only factor contributing to an immunity wall. A large range of factors are at play: population ages, comorbidities (other diseases in the population and how common they are), previous infections, boosters, combined prior infections and boosters, and any other built-in protection for some people against a virus like existing immunity from exposure to the common cold coronavirus.

Because most factors that contribute to a population’s immunity wall cannot be controlled (such as age, prior infection, etc.), experts focus mostly on vaccination efforts to build up an immunity wall. That being said, there is no set point established in science for when an immunity wall has been sufficiently “reached.” Rather, it’s a term used to describe and help us conceptualize all different levels of population protection. An immunity wall, for instance, could be low.

Considering different populations’ immunity walls is important for understanding the current and potential future impact of COVID-19 as well as how the virus may evolve. For instance, one variant may impact one region severely and another more mildly – this is connected to how much immunity is built up.

Context and background

Given that so many people across the world now have some immunity against the COVID-19 virus through infection, vaccination, and exposure, it’s helpful to consider how protected a population is. There are many factors that go into this level of protection, and a broad term sometimes used to think about this population protection is an “immunity wall."

Resources

1. Immunity walls(Ground Truths, Eric Topol)
2. SARS-CoV-2 variants of concern and variants under investigation in England (UK Health Security Agency)
3. Covid booster shots up to 75% effective against Omicron, UK study finds (Financial Times)
4. Mayo Clinic Q&A podcast: Building a wall of immunity against COVID-19 (Mayo Clinic)
5. [ANALYSIS] Assessing the COVID-19 immunity wall in the Philippines (Rappler)

Used with Permission from Health Desk, a public health hub that explains emerging COVID-19 science.