Covid-19: Does Sweden have herd immunity?

At the beginning of August I wrote an article about my experiences working as an emergency physician in Stockholm, Sweden during the covid pandemic. For those who are unaware, Sweden never went in to full lockdown. Instead, the country imposed a partial lockdown that was almost entirely voluntary. People with office jobs were recommended to work from home, and people in general were recommended to avoid public transport unless necessary. Those who were over 70 years old, or who had serious underlying conditions, were recommended to limit social contacts.

The only forcible restriction imposed by the government from the start was a requirement that people not gather in groups of more than 50 at a time. After it became clear that covid was above all dangerous to people in nursing homes, an additional restriction was placed on nursing home visits. At no time has there been any requirement on people to wear face masks in public. Restaurants, cafés, hairdressers, and shops have stayed open throughout the pandemic. Pre-schools and schools for children up to the age of 16 have stayed open, while schools for children ages 16-19 switched to distance learning.

My personal experience is that people followed the voluntary restrictions pretty well at the beginning, but that they have become increasingly lax as time has gone on. As a personal example, my mother and my parents-in-law stayed locked up in their homes for the first six weeks or so of the pandemic. After that they couldn’t bear to be away from their grandchildren any longer.

In my earlier article in August, I mentioned that after an initial peak that lasted for a month or so, from March to April, visits to the Emergency Room due to covid had been declining continuously, and deaths in Sweden had dropped from over 100 a day at the peak in April, to around five per day in August.

At the point in August when I wrote that article, I hadn’t seen a single covid patient in over a month. I speculated that Sweden had developed herd immunity, since the huge and continuous drop was happening in spite of the fact that Sweden wasn’t really taking any serious measures to prevent spread of the infection.

So, how have things developed in the six weeks since that first article?

Well, as things stand now, I haven’t seen a single covid patient in the Emergency Room in over two and a half months. People have continued to become ever more relaxed in their behaviour, which is noticeable in increasing volumes in the Emergency Room. At the peak of the pandemic in April, I was seeing about half as many patients per shift as usual, probably because lots of people were afraid to go the ER for fear of catching covid. Now volumes are back to normal.

When I sit in the tube on the way to and from work, it is packed with people. Maybe one in a hundred people is choosing to wear a face mask in public. In Stockholm, life is largely back to normal. If you look at the front pages of the tabloids, on many days there isn’t a single mention of covid anywhere. As I write this (19th September 2020) the front pages of the two main tabloids have big spreads about arthritis and pensions. Apparently arthritis and pensions are currently more exciting than covid-19 in Sweden.

In spite of this relaxed attitude, the death rate has continued to drop. When I wrote the first article, I wrote that covid had killed under 6,000 people. How many people have died now, six weeks later? Actually, we’re still at under 6,000 deaths. On average, one to two people per day are dying of covid in Sweden at present, and that number continues to drop.

In the hospital where I work, there isn’t a single person currently being treated for covid. In fact, in the whole of Stockholm, a county with 2,4 million inhabitants, there are currently only 28 people being treated for covid in all the hospitals combined. At the peak, in April, that number was over 1,000. If 28 people are currently in hospital, out of 2,4 million who live in Stockholm, that means the odds of having a case of covid so severe that it requires in-hospital treatment are at the moment about one in 86,000.

Since March, the Emergency Room where I work has been divided in to a “covid” section and a “non-covid” section. Anyone with a fever, cough, or sore throat has ended up in the covid section, and we’ve been required to wear full personal protective equipment when interacting with patients in that section. Last Wednesday the hospital shut down the covid section. So few true cases of covid are coming through the Emergency Room that it no longer makes sense to have a separate section for covid.

What about the few formal restrictions that were imposed early in the pandemic? The restriction on visits to nursing homes is going to be lifted from October 1st. The older children, ages 16-19, who were engaging in distance learning during part of the spring, are now back in school, seeing each other and their teachers face to face. The Swedish public health authority has recommended that the government lift the restriction on gatherings from 50 people to 500 people.

When I wrote my first article, I engaged in speculation that the reason Sweden seemed to be developing herd immunity, in spite of the fact that only a minority had antibodies, was due to T-cells. Since I wrote that article, studies have appeared which support that argument. This is good, because T-cells tend to last longer than antibodies. In fact, studies of people who were infected with SARS-CoV-1 back in 2003 have found that they still have T-cells seventeen years after being infected. This suggests that immunity is long lasting, and probably explains why there have only been a handful of reported cases of re-infection with covid, even though the virus has spent the last nine months bouncing around the planet infecting many millions of people.

As to the handful of people who have been reported to have been re-infected. Almost all those cases have been completely asymptomatic. That is not a sign of waning immunity, as some claim. In fact it is the opposite. It shows that people develop a functioning immunity after the first infection, which allows them to fight off the second infection without ever developing any symptoms.

So, if Sweden already has herd immunity, what about other countries? How close are they to herd immunity? The places that have experienced a lot of covid infections, like England and Italy, have mortality curves that are very similar to Sweden’s, in spite of the fact that they went in to lockdown. My interpretation is that they went in to lockdown too late for it to have any noticeable impact on the spread of the disease. If that is the case, then they have likely also developed herd immunity by now. Which would make the ongoing lockdowns in those countries bizarre.

What about the vaccine? Will it arrive in time to make a difference? As I mentioned in my first article, lockdown only makes sense if you are willing to stay in lockdown until there is an effective vaccine. Otherwise you are merely postponing the inevitable. At the earliest, a vaccine will be widely available at some point in the middle of next year. How many governments are willing to keep their populations in lockdown until then? And what if the vaccine is only 30% effective? Or 50%? Will governments decide that is good enough for them to end lockdown? Or will they want to stay in lockdown until there is a vaccine that is at least 90% effective? How many years will that take?

So, to conclude: Covid is over in Sweden. We have herd immunity. Most likely, many other parts of the world do too, including England, Italy, and parts of the US, like New York. And the countries that have successfully contained the spread of the disease, like Germany, Denmark, New Zealand, and Australia, are going to have to stay in lockdown for at least another year, and possibly several years, if they don’t want to develop herd immunity the natural way.

You might also be interested in watching the interview I did with Sky News about covid-19 or reading my article about the role of vitamin D in treating covid-19.

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Author: Sebastian Rushworth, M.D.

I am a practicing physician in Stockholm, Sweden. I studied medicine at Karolinska Institutet (home of the Nobel prize in medicine). My main interests are evidence based medicine, medical ethics, and medical history. Every day I get asked questions by my patients about health, diet, exercise, supplements, and medications. The purpose of this blog is to try to understand what the science says and to translate the science in to a format that non-scientists can understand.

106 thoughts on “Covid-19: Does Sweden have herd immunity?”

  1. Thank you for this article, Dr Rushworth. I have become an avid reader of your blog since your early August post regarding the possibility of herd immunity in Sweden and I had been considering sending you an email asking if you would bring us up to date about what has been transpiring in the weeks since. I live in Maine and the American press still reports the “disastrous” and “catastrophic” outcome in Sweden as part of an simply astonishing barrage of manipulated, “cherry picked” information that remains devoid of scientific truth and is clearly meant to divide us politically as the presidential election approaches. It has been exceedingly difficult in the U.S. to find science-based, unbiased information about Covid and your blog has become an important resource for me. Thank you for writing it—I look forward to your next post.

  2. Thank you for keeping us up to date with truths. People like yourself and Malcolm Kendrick are a breath “unmasked “ fresh air. Keep up the good work

  3. Maybe in Stockholm there is a degree of immunity. But there have not been many cases here in the South of Sweden, I cannot see how there could be immunity here. Yet there are few cases and practically no hospitalizations here either. Although behaviour is as normal as in Stockholm.

  4. Thank you for your very interesting article and I am glad that Sweden has developed herd immunity. I am not sure that it is the case yet in the UK. We locked down a bit late so hopefully parts of the UK have some herd immunity but case numbers are currently rising rapidly again. So far the death rate has only risen a small amount, which is hopeful, but this is probably because most of the cases are in younger age groups. The elderly and those with underlying health conditions now know better how to avoid infection. The next few weeks will tell if the death rate is going to rise rapidly again. Hopefully it is just a case of those who did not get Covid in the first wave are now developing herd immunity while the vulnerable are trying to avoid infection.

  5. The expression ‘herd immunity’ has unfortunate overtones for some. If the french version, ‘community immunity’ (immunité communautaire) were used, it might be easier to sell to the public.

  6. Thank you doctor! Please, keep us inform about herd immunity in Sweden as seems that our authorities do not agree that it is true.
    One more thing. I saw this study, published 2 days ago in BMJ and on last part I saw this: ”
    Theoretically, the placebo arm of a covid-19 vaccine trial could provide a straightforward way to carry out such a study, by comparing the clinical outcomes of people with versus those without pre-existing T cell reactivity to SARS-CoV-2. A review by The BMJ of all primary and secondary outcome measures being studied in the two large ongoing, placebo controlled phase III trials, however, suggests that no such analysis is being done”
    Does it means that if volunteers included in the trial 3 are not tested before vaccine administration if they have pre-immunity(based on T-cell) and they might test only for antibody the result of vaccine do produce false efficiency status ? The person was already immune, does exist the chance to assume in trial reports that vaccine did created the immunity ?
    I do not have medical background so not sure if my understanding is correct.
    Here it is the study: https://www.bmj.com/content/370/bmj.m3563

    1. HI,
      The results of a trials shouldn’t be affected in terms of showing efficacy, since randomization should result in equal numbers with existing T-cell immunity in both groups. But it would be useful to have data pre-vaccination and post-vaccination on how many have Covid specific T-cells, since that would help to determine what effects the vaccine has. It’s a shame that the vaccine studies are not including that information.

  7. Hi Sebastian, I am the editor of The BFD in NZ. I am writing to request your permission to republish this article on The BFD. I would give full attribution and two links back to your site, one at the start of the article and one at the end.

  8. I agree for Sweden but UK, France and Spain locked down a bit earlier so now the wave raise again. Please, check and update your article otherwise won’t be trusted by public neither in Sweden matter. Or if the intention was to say parts of UK, France and Spain have herd immunity and not entire country as a whole, please mention this.
    Very glad for the news, keep up the good work you do!

  9. It is true that Spain locked down relatively early when compared to the UK for example. But only after they had allowed nationwide demonstrations go ahead only days prior where 100s of thousands took to the streets to protest about an unrelated matter. It ater transpired that some protesters were already infected and barely a mask in sight, such as it was then.

  10. I so wish the Spanish government would read this and finally understand how health works. it’s so frustrating how they keep on imposing lockdowns and like you said, are they waiting for a vaccine? it’s so damaging for everyone’s mental and emotional health that I think we’ll have a much bigger crisis to deal with than just an economic one after this is ‘over’. thank you for informing us. I’ll send it to as many people as I can!

  11. Thank you for another great post. Your articles explain the situation simply and without bias on what’s going on on the ground. They are a breath of fresh air to read, and make so much sense. I hope the rest of the world follow’s Sweden’s example soon.

  12. Dear Sebastian, very good article. I am living around 8 month a year in Spain (Mallorca) and I was there into the first lockdown. I would not agree that Spain was able to develop herd immunity. The infection rate at the time of lockdown i.e. in the balearic islands was too low and too few were being infected.. But I do have a theory or a question: In Spain there is one of the strictest mask wearing regulation all over the world, and there are very high case rates. Yesterday I was in a supermarket and watched to all the people wearing masks. What I have recognized was that the mask and face touching numbers are increasing if the people are wearing masks during a daily process. Under your perspective, could it be, that wearing masks incorrectly, and the wear of masks correctly is for normal people nearly impossible to handle, can increase the spread of a virus ?

  13. Hey Sebastian,
    Thanks for writing these articles. I find it absolutely fascinated to read about life in Sweden at the moment. One thing that is talked about a lot here in the media in the US is how we don’t know the long term impacts of the virus. All of the people, including young people, who have post covid symptoms that don’t seem to get better. What’s your take on this in Sweden? If Sweden has reached herd immunity then certainly there should be a lot of people suffering from these post covid symptoms? I would love to hear your opinion? Do you think the Swedish population is just generally healthier? Do these people with post covid not present themselves to the hospital system? thanks in advance for your thoughts!

    1. Hi Ryan,
      I think this “long covid” is blown out of proportion by the media. Post viral syndrome, i.e. lingering symptoms after a viral infection is nothing new, we see it with many viral respiratory infections. The vast majority of people recover completely within a few months.

  14. Hi Dr Rushworth

    Your article indirectly criticizes Germany, Denmark, Australia and NZ for not trying to develop “herd Community” to their people like Sweden did. But let’s look at the figures as on today:

    Sweden
    Cases per million: 8,725
    Death per million: 580
    Test per million: 137,757

    Germany
    Cases per million: 3,262
    Death per million: 113
    Test per million: 173,623

    So, by calculating population of these countries; Germany’s death number should reach 48,000 to matches Sweden’s pro-rata’s death! That is 40,000 more death (now they have 9,000 death only).

    New Zealand
    Cases per million: 383
    Death per million: 5
    Test per million: 182,094

    by also calculating population of these countries; NZ’s death number should reach 2,900 to matches Sweden’s pro-rata’s death! That is 2,875 more death (now they have 25 death only)!!

    That’s why, I think, Germany and NZ and maybe many other countries would think more than once before listening to these suggestions!

    1. Hi Salah,
      I’m not criticizing those countries. I am saying that they will have to get to herd immunity one way or another. Either the natural route, which they can do now, by letting the disease spread among the healthy population while protecting risk groups, or by vaccine, which means staying in lockdown for at least another year, and more likely several years, if they want a vaccine that is over 90% effective.

  15. Sebastian I’d also ask you – do you have any information on the frequency of lasting post covid symptoms? The frequency of lasting post covid seems to me to be a critical point for evaluating what is the better approach.

    1. Hi John, I’m not aware of any good studies of this yet. But post viral syndrome is nothing new, and the vast majority of people recover within a few months. As far as I can see from personal experience, it is a small minority of people who continue to have lingering symptoms for a few months after infection. I am aware of one such case in my immediate surroundings, and that person has now recovered completely.

  16. Sebastian,

    Thank You for sharing Your experience and knowledge.

    If Sweden has herd immunity with less then 10 % antibodies. How can this study in Iceland be
    explained?

    https://www.nejm.org/doi/full/10.1056/NEJMoa2026116

    Would be very interesting to hear Your thoughts about that:

    m pretty sure alot of people does not develop antibodies, to many people I know had covid symptoms in march/april. Quite a few with and quite a few without antibodies, despite similiar symptoms. In some cases even in the same family.

    1. Hi Jonas,
      The sicker someone has been, the more likely they are to have antibodies. This has been shown in multiple studies. Among the people who are so sick that they need hospitalization, most people end up having antibodies. Among people who are asymptomatic or so lightly symptomatic that they don’t bother to visit a health care provider, few have antibodies. But even the ones who don’t develop antibodies do seem to develop T-cells. See this:

      https://sebastianrushworth.com/2020/08/08/what-is-the-best-way-to-measure-rates-of-covid-immunity/

  17. Dr Rushworth, Some countries contained the virus without a hard lockdown, e.g. South Korea, Taiwan, Thailand, Germany and Iceland. They managed without high number of deaths in the first round and still a second wave of deaths is not seen. How should those countries be understood in this context?

    1. Hi Håkan,
      I don’t know enough about Taiwan or Thailand to comment. When it comes to South Korea, Germany, and Iceland, I think they have been able to contain it without as repressive measures as many other countries thanks to the fact that they were doing widespread and effective tracking and tracing from the start. Iceland obviously has the additional advantage of being a small island, which makes it easier to control the new infections coming in to the country.

  18. I do not want to come ahead of Sebastian, but I think your question has an internally answer. A lot of countries who went into a strange lockdown just at the beginning of the pandemic could have luck with a early adopting secure vaccine or have some worse time and figures in front of them. I would say that is what he in my view wants to tell us.

    1. As I’ve said before, cases are meaningless. The only statistic that matters is deaths, which continue to remain at a low level. If the test has a 1% false positive rate, and only one in a thousand people tested actually has the infection, then 9 out of 10 positive cases is a false positive. When the disease is rare, as it is now in the UK, you get many more false positives than true positives. See this:

      https://www.spectator.co.uk/article/how-many-covid-diagnoses-are-false-positives-

  19. “I engaged in speculation that the reason Sweden seemed to be developing herd immunity, in spite of the fact that only a minority had antibodies, was due to T-cells.”

    What’s not explained is why other countries don’t have this herd immunity thanks to T-cells.
    There are many countries or places that had higher per capita case rates and death rates than Sweden. Yet those countries don’t seem to have any “herd immunity” and are experiencing second waves.
    Why? Is Sweden the only country in the world with T-cell immunity from cross reactive coronavirus infections? That’s implausible.

    1. Like I said in the article, I think the countries like England that have experienced a lot of deaths also have herd immunity by now. The rise in cases in England at the moment does not reflect a rise in true cases, only a rise in testing and thereby false positives. Note that deaths in England are remaining at a low stable level, indicative of herd immunity.

  20. They can’t. Unfortunately their experience contradicts the “herd immunity” concept as applied to Sweden, but I’ve no doubt that Sebastian will come up with some contrived explanation that has been made to fit his hypothesis, which is not how scientists should consider explanation of observations.

  21. Sebastian, your presumption is that a vaccine will take another year… but several will likely be available in the first part of next year.

    Your presumption is also that a vaccine needs to be 90% effective. It doesn’t. If we assume that populations have some natural immunity to begin with, and you only need 50-60% as your herd immunity threshold, then you need maybe an additional 30% immunity from a vaccine.
    If it’s only 50% effective, this can be achieved with vaccination of 60% of susceptibles.

    1. Being available is not the same thing as being widely available. Although there will likely be some vaccines available at the beginning of the year, it will take at least until the middle of the year before they are widely available for mass vaccination to be feasible.

  22. I don’t. They have significant economic downturn, more than their Scandinavian neighbours, and 10 times as many deaths as Norway and Finland pro rata.
    If you want a model to follow, try Norway.

  23. Have been wondering if lasting aftereffects of all kinds of viral infections is nothing new, rather that its the first time they’ve gotten this much attention.

  24. Michel the UK is seeing a rise in the numbers of people testing positive but no matching rise in deaths and hospital admissions .

  25. Michael, you missed some points in regards with vaccine:
    1. The population does not trust this vaccine made in rush, so hardly will find 60% to vaccinate;
    2. As usually vaccines do, are less effective for elderly due to luck of immune response;
    3. In adult vaccination, how we know that we do not overlap vaccination on people which has already immunity due to T-cell but has been completely asymptomatic and they are not aware that are already immunized. So, this overlap, which might be huge by the time when vaccine will be wildly available, will make vaccine immunization path even less a good choice.

  26. Using your stance as a hypothesis, what is your null condition? In other words, under what condition(s) would you say “I was wrong”? For example. if ICU rates increase beyond those at the previous peak [and] travel restrictions remain (local transmission), would that qualify? Any other possible outcomes which would invalidate your stance?

    1. Hi, if the death rate and/or ICU admission rate returns to the level it was at at the beginning of July, i.e. 10-20 deaths per day, then I will say that I was wrong about herd immunity. At the peak the death rate was 110-120, so I am willing to concede defeat at a much lower level than the peak rate.

  27. Sebastian hi!
    I agree with your latest article. You and your followers ought to be interrested in the report from the region of Östergötland dated 06082020. Journals of 240 people which died WITH CV-19, turned out 15% to died OF CV-19: 15% died of some other disease: 70% had several diseases, among them CV-19. 50% of the died was 88 years or older
    So, why are media only publishing death rates of people dying WHITH CV-19? news paper in Sweden doesn´t write mush anymore, but public service are still on the chopping block.

    A report from OXFAM is also fearsome: 120 000 000 miljones of people are threatened of starvation – because of the lockdowns!

  28. With respect, Dr. Rushworth, the claim that the number of deaths is the only statistic that matters suggests a surprising lack of awareness of the significant numbers of people who have experienced serious, long-term degradations of health, and what that implies.

  29. Hi! What about that herd immunity and individual immunity? I think there is some missunderstanding as I think for herd immunity at least 50% of population must be immunized for this desease and take many years to achive this. In Sweden as I know there is no such evidence and we must wait to see how next waves will hit this country for some confirmation.

  30. Thank you for this detailed information. I live in Sun Valley, Idaho in the US. We have a lot of sickness and some death in March and few cases since. At one point we had the most cases per capita in the US. Unfortunately, our children are still not allowed in school full time and our entire community is hysterical with fear. I will pass this along to as many people who will listen.

  31. Well said! Should we really listen to the theories of a junior doctor who only qualified this January and fails to explain major facts relating to Sweden’s population density instead of experienced virologists? It’s interesting how right wing publications have shared his articles!

    1. If you are the kind of person who only listens to old doctors with several decades experience, then I can recommend you turn to Malcolm Kendrick or Johan Giesecke. Personally, I think the strength of an argument matters more than the age of the person making it.

  32. I think Dr Rushworth has done a terrific job in presenting evidence based facts on his blog in plain language comprehensible for us laymen. And so far most commentators have shown good manners. Please, let’s keep it that way and skip the politics. Facts don’t care about politics, facts are just facts.

  33. @suddyan.

    There is no scientific argument, that’s why.
    A lot of questions, maybes, ifs and general supposition.
    No conclusion to match the headline.

  34. Dr. Rushworth: Dr. Kendrick is not old, just comfortably middle-aged. Like you, he is a truth-teller. Something tells me there are plenty more physicians who are truth-tellers but whose voices are not-often-enough heard.

  35. Hakan: Thank you. It is appalling the way so much has been politicized in the U.S. by those who hate Trump, including demonizing HCQ + zinc as a treatment, which many doctors have used to save many lives. Politics has no place here. Dr. Rushworth is sharing with us the fruits of his knowledge and experience of the ‘Rona in Sweden, which is invaluable to all of us wherever we live.

  36. The conclusion that Sweden has herd immunity seems to be based on one physician’s observations of few people in the emergency room. What about the prevalence of antibodies to Covid-19, if you are a proponent of “evidence based medicine” shouldn’t that weigh into such a conclusion? It disturbs me immensely to see so many “experts” claiming much higher rates based on NOTHING. How can you make a claim like herd immunity when the antibody prevalence rate remains only 17%?

    Important to also stress to all the Americans on this board that Sweden is not America– they have free access to health care and much better health outcomes than Americans do…They are also much smarter than much of America; if told to wear masks and stay home, they do! I’ll bet you they aren’t having big rallies in arenas like your current President is. Many also disappeared to their summer homes for the summer which could be an explanation for the drop in mortality. They are also not nearly as fat as Americans and have a much lower rate of pre-existing conditions associated with mortality. So if it is mortality that is driving the conclusions here, don’t assume that what Sweden did can or should be replicated in the United States…

  37. Here in the US, if any term like herd immunity, or drug, or anything, is mentioned by the president, the entire mainstream media gets together to plan out a coordinated strategy to dismiss it, bash it, or worse – get the FDA to ban it (think hydroxychloroquine). Sadly, honesty is not allowed in the US anymore as bigPharma has a trillion dollar profit agenda and all of their puppets are working hard to make sure that fear remains, that nobody gets exposed (and thus gets better and immune), and that everyone is still clamoring for a vaccine when it finally becomes available. And heaven forbid you mention how well Sweden is doing. You might as well say that Hitler was a great guy. You get the same reaction. Money has controlled this from the beginning. How Sweden was lucky enough to have politicians that did the right thing is something we will hopefully learn. Until then, the insanity will continue along with the non-stop lies and fearmongering.

  38. Ah! The USA’s “National Treasure” Dr. Fauci, who through the NIH funded “Gain of Function” research at the Wuhan Lab, with tax payer money after it being banned in 2014. When will the MSM ask the good OLD doctor about that. Crickets on that little bit of information being withheld from the tax paying American citizenry.

    Every person concerned with this should do their due diligence on “Gain of Function” virus manipulation and the Wuhan Lab.

    With that random troller’s are here to discredit the Doctor… why? People on this blog are reading to hear the front line experience of a Medical Doctor. Were any of these trolls, attempting to divert the conversation on the front lines? Or are they regurgitating from a script provided to them by the Bill & Milanda Gates foundation and their brought and paid for cronies. We all know who they are.

    To the trolls, you can keep trying to suppress the success of the Swedish Model of guiding their citizenry thru this with humanity, civility and foresight, but not for long. I plan to share the good Doctors information with each and every person I know.

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