• Profile
Close

COVID-19: Herd immunity threshold could be lower, study finds

ScienceDaily Jun 30, 2020

Herd immunity to COVID-19 could be achieved with fewer people being infected than previously estimated, according to new research.

For our comprehensive coverage and latest updates on COVID-19 click here.

Mathematicians from the University of Nottingham and University of Stockholm devised a simple model categorising people into groups reflecting age and social activity level. When differences in age and social activity are incorporated in the model, the herd immunity level reduces from 60% to 43%. The figure of 43% should be interpreted as an illustration rather than an exact value or even a best estimate. The research has been published today in Science.

Herd immunity happens when so many people in a community become immune to an infectious disease that is stops the disease from spreading. This happens by people contracting the disease and building up natural immunity and by people receiving a vaccine. When a large percentage of the population becomes immune to a disease, the spread of that disease slows down or stops and the chain of transmission is broken.

This research takes a new mathematical approach to estimating the herd immunity figure for a population to an infectious disease, such as the current COVID-19 pandemic. The herd immunity level is defined as the fraction of the population that must become immune for disease spreading to decline and stop when all preventive measures, such as social distancing, are lifted. For COVID-19 it is often stated that this is around 60%, a figure derived from the fraction of the population that must be vaccinated (in advance of an epidemic) to prevent a large outbreak.

The figure of 60% assumes that each individual in the population is equally likely to be vaccinated, and hence immune. However, that is not the case if immunity arises as a result of disease spreading in a population consisting of people with many different behaviours.

Professor Frank Ball from the University of Nottingham participated in the research and explains: "By taking this new mathematical approach to estimating the level for herd immunity to be achieved we found it could potentially be reduced to 43% and that this reduction is mainly due to activity level rather than age structure. The more socially active individuals are then the more likely they are to get infected than less socially active ones, and they are also more likely to infect people if they become infected. Consequently, the herd immunity level is lower when immunity is caused by disease spreading than when immunity comes from vaccination.

Our findings have potential consequences for the current COVID-19 pandemic and the release of lockdown and suggests that individual variation (e.g. in activity level) is an important feature to include in models that guide policy."

Go to Original
Only Doctors with an M3 India account can read this article. Sign up for free.
  • 55 lakhs+ doctors trust M3 globally

  • Nonloggedininfinity icon
    Unlimited access to original articles by experts
  • Nonloggedinlock icon
    Secure: we never sell your data
  • Signing up takes less than 2 mins
Try M3 India / Log In
x
M3 app logo
Choose easy access to M3 India from your mobile!


M3 instruc arrow
Add M3 India to your Home screen
Tap  Chrome menu  and select "Add to Home screen" to pin the M3 India App to your Home screen
Okay