dotlah! dotlah!
  • Cities
  • Technology
  • Business
  • Politics
  • Society
  • Science
  • About
Social Links
  • zedreviews.com
  • citi.io
  • aster.cloud
  • liwaiwai.com
  • guzz.co.uk
  • atinatin.com
0 Likes
0 Followers
0 Subscribers
dotlah!
  • Cities
  • Technology
  • Business
  • Politics
  • Society
  • Science
  • About
  • People
  • World Events

How many people need to get a COVID-19 vaccine in order to stop the coronavirus?

  • January 17, 2021
pandemic-crowd-macau-photo-agency-4yXV0JIK-yo-unsplash
Total
0
Shares
0
0
0

It has been clear for a while that, at least in the U.S., the only way out of the coronavirus pandemic will be through vaccination. The rapid deployment of coronavirus vaccines is underway, but how many people need to be vaccinated in order to control this pandemic?

I am a computational biologist who uses data and computer models to answer biological question at the University of Connecticut. I have been tracking my state’s COVID-19 epidemic with a computer model to help forecast the number of hospitalizations at the University of Connecticut’s John Dempsey Hospital.

Before the U.S. can return to some form of normal, a lot of people need to be vaccinated.
AP Photo/Paul Sancya, Pool

This type of computer model and the underlying theory can also be used to calculate the vaccination rates needed to break the chain of transmission of the coronavirus. My estimate is that for the entire U.S., roughly 70% of the population needs to be vaccinated to stop the pandemic. But variation in how people behave in different parts of the country, as well as open questions on whether the vaccine prevents infection entirely or just prevents people from getting sick, add a degree of uncertainty.

A drawing showing a circle of green happy faces with some blue happy faces in the middle and a red frowning face unable to reach the blue faces.
When enough people are vaccinated, the coronavirus will not be able to spread from person to person.
Cavernia via Wikimedia Commons, CC BY-SA

Cutting off transmission

Clinical trials have shown that once a person gets vaccinated for the coronavirus, they won’t get sick with COVID-19. A person who doesn’t get sick can still be infected with the coronavirus. But let’s also assume that a vaccinated person can’t spread the virus to others, though researchers still don’t know if this is true.

When enough of the population is vaccinated, the virus has a hard time finding new people to infect, and the epidemic starts dying out. And not everyone needs to be vaccinated, just enough people to stop the virus from spreading out of control. The number of people who need to be vaccinated is known as the critical vaccination level. Once a population reaches that number, you get herd immunity. Herd immunity is when there are so many vaccinated people that an infected person can hardly find anyone who could get infected, and so the virus cannot propagate to other people.
This is very important to protect people who cannot get vaccinated.

The critical vaccination level depends on how infectious the disease is and how effective the vaccine is. Infectiousness is measured using the basic reproduction number – R0 – which is how many people an infected person would spread the virus to on average if no protective measures were in place.

The more infectious a disease is, the larger the number of people who need to be vaccinated to reach heard immunity. The higher the effectiveness of the vaccine, the fewer people need to be vaccinated.

A barn in a field with a city in the background.
Different social behavior in different places leads to varying R0 values.
Ed Freeman/Stone via Getty Images

Not the same everywhere

R0 values differ from place to place because their populations behave differently – social interactions are not the same in rural and urban locations, nor in warm climates compared to cold ones, for example.

Using the data on positive cases, hospitalizations and deaths, my model estimates that Connecticut currently has an R0 of 2.88, meaning that, on average, every infected person would pass the virus on to 2.88 other people if no mitigation measures were in place. Estimates at the county level range from 1.44 in rural Alpine, California to 4.31 in urban Hudson, New Jersey.

But finding an R0 value for the entire U.S. is especially tricky because of the diversity of climates and because the virus has affected different areas at different times – behavior has been far from uniform. Estimates vary from 2.47 to 8.2, though most researchers place R0 for the entire U.S. around 3.

While R0 varies by location and between estimates, the effectiveness of the vaccines is constant and well known. The Pfizer-BioNTech and Moderna vaccines are 95% and 94.5% effective at preventing COVID-19, respectively.

Using values for vaccine effectiveness and the R0, we can calculate the critical vaccination level. For Connecticut, with an R0 of 2.88, 69% of the population needs to be vaccinated. For the entire U.S., with R0 of 3, this would be 70%. In New York City, with an estimated R0 of 4.26 this would be 80%.

A lot of uncertainty

While the math is relatively simple, things get complicated when you consider important questions for which epidemiologists still have no answers.

A sign in a shop window saying the shop is closed until further notice due to COVID-19
Vaccines offer the best path forward, but a few unknowns could change how many people need to be vaccinated.
Annie Japaud/Moment via Getty Images

First, the formula for critical vaccination level assumes that people interact randomly. But in the real world, people interact in highly structured networks depending on work, travel and social connections. When those contact patterns are considered, some researchers found critical vaccination levels to be considerably smaller compared to assuming random interactions.

Unfortunately, other unknowns could have an opposite effect.

Vaccine trials clearly show that vaccinated people don’t get sick with COVID-19. But it is still unknown whether the vaccines prevent people from getting mild infections that they could pass on to others. If vaccinated people can still be infected and pass on the virus, then vaccination will not provide herd immunity – though it would still prevent serious disease and reduce mortality drastically.

A final question that remains to be answered is how long immunity to the coronavirus lasts after a person is vaccinated. If immunity wanes after a few months, then each individual will need repeated vaccinations.

It is hard to say with certainty how many people need to be vaccinated in order to end this pandemic. But even so, the arrival of COVID-19 vaccines has been the best news in 2020. In 2021, as a large proportion of individuals in the U.S. get the vaccine, the country will be heading toward the critical vaccination level – whatever it may be – so that life can start to return to normal.

The Conversation

Pedro Mendes, Professor of Cell Biology, University of Connecticut

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Total
0
Shares
Share
Tweet
Share
Share
Related Topics
  • AstraZeneca
  • Coronavirus
  • COVID-19
  • COVID-19 Vaccine
  • Herd Immunity
  • Moderna
  • Pfizer
  • Viruses
majulah

Previous Article
  • Cities
  • Lah!

Grab And Panasonic Launch Integrated Campaign To Promote Better Indoor Air Quality In Southeast Asia

  • January 15, 2021
View Post
Next Article
cycling bike
  • Cities
  • People

Why Bicycle Accidents Can Be So Devastating

  • January 18, 2021
View Post
You May Also Like
View Post
  • People
  • Politics

Singapore PM Wong arrives in Malacañang

  • dotlah.com
  • June 4, 2025
college-of-cardinals-2025
View Post
  • Featured
  • Features
  • World Events

The Definitive Who’s Who of the 2025 Papal Conclave

  • Dean Marc
  • May 8, 2025
conclave-poster-black-smoke
View Post
  • Featured
  • Features
  • World Events

The World Is Revalidating Itself

  • Dean Marc
  • May 7, 2025
View Post
  • Featured
  • Features
  • People

Conclave: How A New Pope Is Chosen

  • Dean Marc
  • April 25, 2025
View Post
  • People

PM Wong takes Scoot flight, fellow passengers cheer

  • dotlah.com
  • October 16, 2024
dotlah-pm-lee-lawrence-wong-9656d4cd-1fa4-40ed-905d-e19e639b8476_728802dd
View Post
  • Lah!
  • People
  • Politics

End of Lee Era for Singapore as PM Steps Down

  • dotlah.com
  • May 16, 2024
View Post
  • People
  • Politics

‘A much bigger step forward’: Lawrence Wong on his journey to becoming Singapore’s fourth PM

  • dotlah.com
  • May 15, 2024
DPM Lawrence Wong will be Singapore's fourth prime minister on May 15. ST PHOTO: LIM YAOHUI
View Post
  • Lah!
  • People
  • Politics

7 things to know about Singapore’s next prime minister Lawrence Wong

  • dotlah.com
  • May 15, 2024


Trending
  • 1
    • Lah!
    • Society
    Singapore’s Older Adults Resist COVID-19 Vaccinations
    • July 7, 2021
  • 2
    • Technology
    UOB Taps Chronicle Software’s Solution For Its Electronic FX Pricing And Trade Engine To Help Customers Access More Competitive FX Pricing
    • June 3, 2021
  • london-uk-anthony-delanoix-CFi7_hCXecU-unsplash 3
    • Cities
    The Best Cities for International Students
    • January 20, 2022
  • 4
    • Lah!
    • Science
    • Technology
    5 Space Tech Startups In SEA Paving The Way Beyond
    • May 2, 2020
  • 5
    • Technology
    GovTech Licenses “SPOTON” Software To SMEs & NPO To Produce Smart Thermal Scanners
    • September 19, 2020
  • 6
    • Lah!
    Male Wolbachia-Aedes Mosquito Releases To Cover Entire Yishun And Tampines HDB Towns
    • July 21, 2020
  • driving 7
    • Cities
    Reasons Why Defensive Driving Is A Must
    • October 28, 2020
  • 8
    • Society
    UOB And Prudential Singapore Launch The UOB Lady’s Savings Account To Help Women Grow Their Wealth And Protect Their Health
    • March 10, 2020
  • 9
    • People
    • World Events
    Are We Opening When We Should?
    • June 5, 2020
  • 10
    • Technology
    How Cold War Rivalry Helped Launch The Chinese Computer
    • August 18, 2019
  • 11
    • Lah!
    • Technology
    Singapore Spacer: Mapping Concentrations Of People In Campus Buildings
    • April 8, 2020
  • Medicine 12
    • People
    • Technology
    Drug Resistance: Could Global Goals Be The Answer To This Worldwide Health Crisis?
    • January 19, 2024
Trending
  • 1
    Malaysia’s ‘ASEAN Shenzhen’ needs some significant legal reform to take off — here’s how
    • August 25, 2025
  • French Fries 2
    Air Fryer: The One Cooking Appliance to Rule Them All – Best All-Around Picks in 2025
    • August 22, 2025
  • 3
    Samsung Electronics Debuts Odyssey G7 Monitors, Showcasing Top Games on Its Displays at Gamescom 2025
    • August 20, 2025
  • 4
    HP Cranks Up the Game with Smarter Systems, Cooler Builds, and Gear That Hits Different
    • August 14, 2025
  • 5
    New Trump tariffs: early modelling shows most economies lose – the US more than many
    • August 6, 2025
  • Scuba Diving 6
    Wetsuit or Drysuit? As always, it depends. This quick guide can help you choose.
    • August 2, 2025
  • 7
    Thoughts on America’s AI Action Plan
    • July 24, 2025
  • 8
    Introducing Surface Laptop 5G: Seamless connectivity, built for business
    • July 23, 2025
  • 9
    Press Start (Or Hit Enter)! Your Go-To Loadout for Streamers and Gamers.
    • July 19, 2025
  • 10
    ESWIN Computing launches the EBC77 Series Single Board Computer with Ubuntu
    • July 17, 2025
Social Links
dotlah! dotlah!
  • Cities
  • Technology
  • Business
  • Politics
  • Society
  • Science
  • About
Connecting Dots Across Asia's Tech and Urban Landscape

Input your search keywords and press Enter.