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Can first COVID-19 vaccines bring herd immunity? Experts have doubts

18 Comments
By Ludwig Burger and Kate Kelland

Governments and officials are voicing hopes that COVID-19 vaccines could bring"herd immunity", with some calculating that immunising just two-thirds of a population could halt the pandemic disease and help protect whole communities or nations.

But the concept comes with caveats and big demands of what vaccines might be capable of preventing. Some experts say such expectations are misplaced.

For a start, figuring out what's needed to achieve herd immunity with COVID-19 vaccines involves a range of factors, several of which are unknown.

What is the rate of the spread of the COVID-19-causing virus? Will the first vaccines deployed be able to stop transmission of the virus, or just stop people getting ill? How many people in a population will accept a vaccine? Will vaccines offer the same protection to everyone?

"Herd immunity is sometimes wrongly understood as individual protection," said Josep Jansa, an expert in health emergency preparedness and response at the Stockholm-based European Center for Disease Prevention and Control (ECDC).

"It's inappropriate to think 'I will not be affected myself because there is herd immunity'. Herd immunity refers to community protection, not to how an individual is protected."

The ECDC uses an estimated herd immunity threshold of 67% for its models, while Chancellor Angela Merkel said this month that COVID-19 restrictions in Germany could be lifted if 60% to 70% of the population acquired immunity, either via a COVID-19 vaccine or through infection.

World Health Organization experts have also pointed to a 65%-70% vaccine coverage rate as a way to reach population immunity through vaccination.

"The idea of herd community is to protect the vulnerable," said Eleanor Riley, a professor of immunology and infectious disease at the University of Edinburgh. "And the idea behind it is that if, say, 98% of a population have all been vaccinated, there will be so little virus in the community that the 2% will be protected. That's the point of it."

REPRODUCTION RATE IS CRUCIAL

Central to the public health calculations on this concept for COVID-19 is the reproduction rate, or R value, of the virus that causes it. This is a measure of how many other people an average infected person passes a pathogen on to in "normal", or restriction-free, circumstances.

Assuming complete vaccine efficacy, herd immunity percentage thresholds for infectious diseases are calculated by dividing 1 by the R value, deducting the result from 1, and multiplying by 100.

For instance, herd immunity from highly contagious measles, with an estimated R value of 12 or higher, will kick in only if 92% or more within a group are immune. For a seasonal flu strain that could have an R value of 1.3, the threshold would be just 23%.

"The problem is that for now we don’t know exactly how fast the virus spreads without any precautions and with the normal travel and social activities we had a year ago," said Winfried Pickl, professor of immunology at the Medical University of Vienna.

With so many countries still operating in far from normal circumstances, the assumption should be that the COVID-19 R value would be "closer to 4 than to 2", he said, since even with semi- or full lockdown measures the R value is around 1.5.

Additionally, anything less than 100% vaccine efficacy - such as the 90% or so suggested in early data on the Pfizer-BioNTech and Moderna COVID-19 shots - would require a matching rise in percentage of coverage to reach herd threshold.

Amesh Adalja, a scholar at the Johns Hopkins Center for Health Security, said a good target for immunity in the United States would be for more than 70% of the population to be inoculated, but added that the figure could go up if vaccines are less effective.

STOP TRANSMISSION IN THE "HERD"?

Experts say another important factor is whether the COVID-19 vaccines a government chooses to deploy can stop transmission of the virus.

Evidence so far suggests the first COVID-19 vaccines to come to market will at least stop people developing the disease. But it cannot be ruled out that people will still catch the SARS-CoV-2 virus and pass it on to others unnoticed.

"While protection against illness has a value for an individual, it will not prevent circulation of virus and risk of disease in unvaccinated (people)," said Penny Ward, a visiting professor in pharmaceutical medicine at King’s College London.

Bodo Plachter, a professor and deputy director of the Institute of Virology at Germany's Mainz University teaching hospital, said that respiratory infections in particular can be hard to block completely with vaccines - although the shots will go some way to reducing the amount of circulating virus.

"It may well be that vaccinated people will shed fewer viruses," he said. "But it would be a mistake to assume vaccination alone can suppress a pandemic."

Edinburgh's Riley said this suggests that for now, pursuing an idea of herd immunity through COVID-19 vaccination is fruitless.

A better approach, she said, could be to "turn herd immunity on its head", and use the first limited supplies of vaccines to protect those most in need, without worrying about the more robust members of the "herd" who can live relatively happily with the virus.

"Let's forget about protecting the masses to protect the vulnerable," she said. "Let's directly protect the vulnerable."

© Thomson Reuters 2020.

©2020 GPlusMedia Inc.

18 Comments
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Vaccines are not the only measure, they will come to complement what we have in place and hopefully to replace some of the measures that are more damaging to the economy. The problem is thinking that they will come to replace everything in an instant.

At the beginning there will not be enough doses for everybody, so its natural to think about vaccinating the more vulnerable population first, not to get herd immunity but to get them protected first, not having to depend on the transmission to be completely stopped, afterwards doses can be distributed to everybody else and then you will have everybody individually protected and also transmission stopped in the community protecting those that cannot be vaccinated.

Hopefully the vaccines will also stop asymptomatic transmission, but we cannot take that for granted, so at least at the beginning social distancing measures should still continue until we can know for sure.

4 ( +6 / -2 )

Just letting this "pandemic" run its course will quickly bring about herd immunity. No need for any of these rushed, risky, experimental vaccines.

-9 ( +1 / -10 )

Just letting this "pandemic" run its course will quickly bring about herd immunity. No need for any of these rushed, risky, experimental vaccines.

letting the pandemic "run its course" brings unnecessary complicated patients and deaths, its immoral to choose that option if a safe and effective vaccine, that are not risky nor rushed can avoid it.

4 ( +6 / -2 )

Just letting this "pandemic" run its course will quickly bring about herd immunity. No need for any of these rushed, risky, experimental vaccines.

This is like saying "people will die from Cancer anyways. Why take measures to prevent it or even cure it when someone gets it"?

Talk about first-world entitlement. People in 3rd world countries will line up in droves to take that vaccine. People in sane first-world countries will do the same. Those who think they are smart enough to be able to understand the things they don't, well enough to make an educated decision won't take the vaccine.

5 ( +7 / -2 )

How crazy! You couldn’t even manage that two thirds have installed that cocoa corona app.

-3 ( +1 / -4 )

a safe and effective vaccine, that are not risky nor rushed can avoid it.

Yeah, hopefully we will know whether these vaccines are safe and effective in a few years. But within the next few years, they are too risky.

-4 ( +1 / -5 )

Yeah, hopefully we will know whether these vaccines are safe and effective in a few years. But within the next few years, they are too risky.

That is also a mistaken and immoral position. In a few years we will know more and more details about the vaccines efficacy and safety. But if this year we can know that the vaccines are effective and being vaccinated means having less risk than the natural infection (both in the short and long term) that is enough to justify vaccination.

You "option" of letting people get horrible long term problems or even die, without any need, just because of unjustified, undefined, fuzzy fears about what "may" happen, are unethical. That is why health professionals, that dedicate their lives to examine scientific evidence and apply it for the benefit of human health completely disagree with you.

2 ( +4 / -2 )

The WHO says that 93% to 95% of people need to be vaccinated (or recover from the illness) in order to achieve herd immunity for measles. So, the higher the percentage of people who are immune, the better for those who are not immune.

The discussion of herd immunity for Covid-19 is important, but I will be happy to get the shot(s). If only one person gets vaccinated, then at least that one person is probably safe, since the vaccines in the pipeline appear to be about 95% effective. In other words, it depends on sample size. If the sample is one person, then herd immunity for that sample is achieved with just one vaccination.

As for choosing whether to get vaccinated, that choice offers us a living example of Darwinism at work. If those who decline to get vaccinated are right, then they will pass on a higher percentage of their DNA. If they are wrong, then they will pass on a smaller percentage of their DNA than those who make the opposite decision.

4 ( +4 / -0 )

Definitely correct.

3 ( +3 / -0 )

But if this year we can know that the vaccines are effective and being vaccinated means having less risk than the natural infection (both in the short and long term) that is enough to justify vaccination.

Yeah, if there are no side effects, then indeed getting the vaccine is a good idea. But we won't know for years about the long term side effects. They could be worst than the virus itself. The mRNA vaccine is a new technology.

-5 ( +0 / -5 )

Yeah, if there are no side effects,

No, that is even including side effects. Just the cutoff between phase II and III is enough to prove the vaccine is a much better option than waiting to get infected and run your chances.

We can already see a much more likely probability of long lasting side effects from the natural infection, realistically speaking is would be impossible that thousands of volunteers would all fail to present all the pathological changes that many of the COVID-19 patients already are showing.

Once again, if the risk is less then the vaccine is justified. Even if we had absolutely no information possible about the chances of long term effects. Fortunately we do have it and it points clearly to an even stronger argument for the vaccines.

4 ( +5 / -1 )

No, nobody knows the longterm side effects, including you. Vaccine side effects often take a year or more to show up.

-6 ( +0 / -6 )

No, nobody knows the longterm side effects, including you. Vaccine side effects often take a year or more to show up.

Read again my comment, it is very easy to see pathological changes that will result in long term problems, if those changes are present in infected patients (even on asymptomatic ones) but not on vaccine volunteers it is perfectly valid to say that the chances of having long term effects are hugely more for the infection than from the vaccine. That is enough to justify the vaccine.

Your mistake is automatically assume that COVID-19 can only have acute problems, as if it were a disease that humans had dealt for centuries, it is not. You cannot say that in 5 years from now no patient will end up with cancer, autoimmune diseases or neuronal deterioration because of the infection.

Let me be clear on this, nobody know exactly what will be the long term effects of either, but we can know from now that the natural infection is much more likely to cause them, because of the current effects being observed.

3 ( +4 / -1 )

Let me be clear on this, nobody know exactly what will be the long term effects of either, but we can know from now that the natural infection is much more likely to cause them, because of the current effects being observed.

Humans have been infected by coronaviruses since there have been humans.

Humans have been injected with lipid nanoparticle mRNA vaccines since .... this year (in significant numbers)?

-6 ( +0 / -6 )

Humans have been infected by coronaviruses since there have been humans.

Not with this one, which is why anything you want to predict about his lack of long term effect is just a product of your imagination. How many of the coronaviruses cause pandemias with hundreds of thousands of deaths per year?

Lipid nanoparticles and mRNA are both part of what the body itself produce and deals with continuously. And the artificial versions have been used for many other purposes for years already. Your point is completely invalid, as if using a needle to inject a COVID-19 vaccine would produce some extra problems compared with a needle used to inject other things.

On the other hand non-structural proteins on the virus are part of what the body gets exposed by the infection and that are completely absent from the vaccine. Even thinking on mRNA the infection produces hugely more of that (and that gets transferred between cells on lipid microvescicles) so that alone points to more danger from the infection than from a vaccine.

4 ( +5 / -1 )

Just letting this "pandemic" run its course will quickly bring about herd immunity. No need for any of these rushed, risky, experimental vaccines.

This “pandemic”, which you clearly are too “smart” to believe in, will of course run its course.

But, and it’s a big but, you are wrong to think the best approach is just to wait it out, kiss gramma goodbye and git gud.

Raw Beer? Do you drink Raw Milk straight from the cow’s tit? No, you don’t.

4 ( +5 / -1 )

Once again Virusrex shoots down the conjecture someone who clearly doesn't understand what they are talking about, but is trying to cast doubt on the thing as a whole, rather than educating themselves with the answers to their questions.

"What are the long-term effects, and how can we say there aren't any without long-term testing?" is valid conjecture that I, as well as many others who don't know the answer, would like to know.

"No one knows the long term effects, and it's stupid to take it because of that" is conjecture, and not only useless as far as finding a solution, is counter-productive to society as it casts doubt on the system due to the laziness of the poster to find the answers to their questions.

1 ( +2 / -1 )

On the topic of letting this pandemic just run its course, instead of developing and using a vaccine:

The 1918 pandemic started in January 1918. There were many deaths in the first half of 1918 due to that contagion, but the second half of the year was much worse than the first half. We are seeing something similar play out in 2020, with the current pandemic.

While there were millions of worldwide casualties to the pandemic in 1918, 1919 was much worse. This is a matter of historical record. The point here is that without a vaccine we are on track to repeat what happened a hundred years ago. With the vaccines, many millions of lives will be saved, most likely.

For the sake of accuracy, 1920 did not have as many fatalities from the pandemic as did 1919, but there were still many deaths even after two years. We have a chance to avoid what our forebears went through a hundred years ago.

Repeating myself, but if I may: I grew up often hearing stories from my mother about growing up and living through the 1918 pandemic, in New York City. I won't recount those stories, again, but what she saw obviously traumatized her, and scared the you-know-what out of me, growing up. At least, I thought to myself, we will never have to go through that again. Wow, was I wrong.

1 ( +2 / -1 )

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