WHO's Science in 5 on COVID-19 - Herd Immunity - 28 August 2020

Summary

In this episode of Science in Five, Dr. Samya Swaminathan, WHO’s Chief Scientist, explains herd immunity in the context of COVID-19. She contrasts it with measles, where a 95% vaccination rate is required to achieve herd immunity. For COVID-19, she suggests that around 60-70% immunity is needed, emphasizing that trying to achieve this through natural infection would lead to significant human cost. Dr. Swaminathan advocates for achieving herd immunity safely through vaccination, alongside public health measures like physical distancing, mask-wearing, and testing to prevent the spread of the virus.

Takeaways

• 😀 Herd immunity is achieved when a large percentage of a population is immune to a disease, preventing its spread, even if some individuals remain susceptible.
• 😀 For measles, about 95% of the population needs immunity for herd immunity to be effective, which helps prevent the disease from spreading to those who aren't vaccinated.
• 😀 In the context of COVID-19, the goal is to achieve herd immunity through vaccination rather than natural infection, as letting the virus spread unchecked would lead to widespread illness and death.
• 😀 SARS-CoV-2, the virus that causes COVID-19, is highly transmissible, and it's estimated that 60-70% of the population needs immunity to stop its transmission.
• 😀 Allowing COVID-19 to spread naturally could lead to a significant number of deaths globally, even with a low mortality rate, making it an unsafe strategy for achieving herd immunity.
• 😀 Vaccination is the safest way to achieve herd immunity, as it provides immunity without the harmful effects of natural infection, preventing preventable deaths.
• 😀 Public health measures such as physical distancing, mask-wearing, frequent handwashing, and isolating infected individuals are crucial for slowing transmission of COVID-19 until a vaccine is available.
• 😀 Effective testing, rapid detection of infections, and contact tracing are essential to managing and controlling COVID-19 spread, even in the absence of a vaccine.
• 😀 Achieving herd immunity through vaccination can save lives and reduce the strain on healthcare systems, avoiding unnecessary deaths that could occur if infections were allowed to spread unchecked.
• 😀 Despite the challenges, it is important to continue implementing public health measures, as they can significantly slow the spread of the virus and protect vulnerable populations.

Q & A

What is herd immunity?

Herd immunity occurs when a large portion of the population becomes immune to an infectious disease, either through vaccination or previous infection, making its spread unlikely. For diseases like measles, around 95% immunity is needed to stop transmission.

How does herd immunity work with vaccines?

With vaccines, herd immunity is achieved by vaccinating enough individuals, creating a protective barrier in the community. This prevents the virus from spreading widely even if some people are not immune.

What percentage of the population needs immunity to stop COVID-19 transmission?

For COVID-19, it is believed that around 60-70% of the population needs to have immunity to break the chain of transmission effectively.

Why is it dangerous to let COVID-19 spread naturally to achieve herd immunity?

Allowing COVID-19 to spread naturally could lead to significant collateral damage, including a high number of deaths. Even if only 1% of people infected with COVID-19 die, this percentage becomes substantial when applied to the global population.

What is the preferred method for achieving herd immunity for COVID-19?

The preferred method is through vaccination, as it allows immunity to be achieved safely, without the risk of widespread illness and death associated with natural infection.

Can we slow down the spread of COVID-19 without a vaccine?

Yes, we can slow down transmission by implementing public health measures such as physical distancing, wearing masks, frequent handwashing, and ensuring sufficient testing, isolation, and contact tracing.

What are the public health measures recommended to prevent COVID-19 transmission?

Public health measures include physical distancing, wearing masks in crowded settings, frequent handwashing, rapid testing, isolating infected individuals, and contact tracing.

Why is it important to detect and diagnose COVID-19 cases quickly?

Early detection and diagnosis allow for the isolation of infected individuals and the identification of contacts, which can prevent further transmission of the virus.

What role do vaccines play in preventing COVID-19 deaths?

Vaccines are key in preventing deaths by helping people build immunity against the virus, thus reducing the severity of illness and preventing widespread fatalities.

How do public health measures help while waiting for a vaccine?

Public health measures, such as physical distancing and masks, help reduce transmission rates and protect vulnerable populations while we await vaccines and more effective treatments.