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Saturday 10 June 2023 Dublin: 15°C
Sasko Lazarov via Chief Medical Officer Dr Tony Holohan
# Coronavirus
CMO says herd immunity concept is 'something that's reserved for policy thinking around vaccination'
The concept has been frequently referenced since the beginning of the pandemic.

CHIEF MEDICAL OFFICER Dr Tony Holohan has said the application of herd immunity as a “serious health policy” in relation to Covid-19 “has no substance”. 

The concept has been frequently referenced since the beginning of the pandemic, and suggests that lockdowns could be avoided by allowing the virus to spread amongst communities while putting in safeguards to protect those most at risk.

The hope is that, eventually, a natural immunity to the disease is developed.

Earlier this month, the head of the World Health Organization Tedros Adhanom Ghebreyesus warned against the herd immunity concept and pointed out that the process has never been used as a strategy for responding to an outbreak, let alone a pandemic. 

“Herd immunity is a concept used for vaccination, in which a population can be protected from a certain virus if a threshold of vaccination is reached,” he said.

For measles, for instance, it is estimated that if 95% of the population is vaccinated, the remaining five percent will also be protected from the spread of the virus. For polio, the threshold is estimated at 80%.

“Herd immunity is achieved by protecting people from a virus, not by exposing them to it,” Tedros said.

Speaking at this evening’s press briefing at the Department of Health, Dr Holohan said the argument for herd immunity in relation to Covid-19 has “many, many flaws”.

“We think there really is no substance at all in policy terms to the advocacy around a herd immunity strategy,” Dr Holohan said.

He noted that many people who are most at risk in society would still need to be in contact with people within the community who look after them and provide services. 

Dr Holohan echoed Tedros’ comments and said “the concept of herd immunity is something that’s reserved for policy thinking around vaccination”. 

“The theory here is that if enough people have this vaccination then you, as an individual, have very little risk of picking it up from somebody else if everybody else has been vaccinated,” he said. 

“Its application in this environment as a serious health policy has no substance to recommend it,” he added.

In the early days of Covid-19, it appeared the UK government was pursuing such a strategy but that quickly changed as lockdown measures were introduced amid a sharp spike in cases, hospitalisations and deaths. 

The National Public Health Emergency Team’s epidemiological modelling advisory group chair Professor Philip Nolan recently said there was no guarantee herd immunity would work and is ethically questionable.

Speaking earlier this month, Tedros said that relying on naturally obtaining herd immunity in such a situation would be “scientifically and ethically problematic”.

“Allowing a dangerous virus that we don’t fully understand to run free is simply unethical. It’s not an option.”

He pointed to the lack of information on the development of immunity to Covid-19, including how strong the immune response is and how long antibodies remain in the body.

Tedros pointed to some cases where people are believed to have been infected with the virus a second time.

He also stressed the many long-term health problems of infection, which researchers are only just beginning to understand.

And he pointed out that it has been estimated that less than 10% of the population in most countries are believed to have contracted the disease.

With reporting by © AFP 2020

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