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COVID-19 Vaccines Protect the Family, Too

Posted on by Dr. Francis Collins

Multigenerational family walks at the beach
Credit: Shutterstock

Any of the available COVID-19 vaccines offer remarkable personal protection against the coronavirus SARS-CoV-2. So, it also stands to reason that folks who are vaccinated will reduce the risk of spreading the virus to family members within their households. That protection is particularly important when not all family members can be immunized—as when there are children under age 12 or adults with immunosuppression in the home. But just how much can vaccines help to protect families from COVID-19 when only some, not all, in the household have immunity?

A Swedish study, published recently in the journal JAMA Internal Medicine, offers some of the first hard figures on this topic, and the findings are quite encouraging [1]. The data show that people without any immunity against COVID-19 were at considerably lower risk of infection and hospitalization when other members of their family had immunity, either from a natural infection or vaccination. In fact, the protective effect on family members went up as the number of immune family members increased.

The findings come from a team led by Peter Nordström, Umeå University, Sweden. Like in the United States, vaccinations in Sweden initially were prioritized for high-risk groups and people with certain preexisting conditions. As a result, Swedish families have functioned, often in close contact, as a mix of immune and susceptible individuals over the course of the pandemic.

To explore these family dynamics in greater detail, the researchers relied on nationwide registries to identify all Swedes who had immunity to SARS-COV-2 from either a confirmed infection or vaccination by May 26, 2021. The researchers identified more than 5 million individuals who’d been either diagnosed with COVID-19 or vaccinated and then matched them to a control group without immunity. They also limited the analysis to individuals in families with two to five members of mixed immune status.

This left them with about 1.8 million people from more than 800,000 families. The situation in Sweden is also a little unique from most Western nations. Somewhat controversially, the Swedish government didn’t order a mandatory citizen quarantine to slow the spread of the virus.

The researchers found in the data a rising protective effect for those in the household without immunity as the number of immune family members increased. Families with one immune family member had a 45 to 61 percent lower risk of a COVID-19 infection in the home than those who had none. Those with two immune family members enjoyed more protection, with a 75 to 86 percent reduction in risk of COVID-19. For those with three or four immune family members, the protection went up to more than 90 percent, topping out at 97 percent protection. The results were similar when the researchers limited the analysis to COVID-19 illnesses serious enough to warrant a hospital stay.

The findings confirm that vaccination is incredibly important not only for individual protection, but also for reducing transmission, especially within families and those with whom we’re in close physical contact. It’s also important to note that the findings apply to the original SARS-CoV-2 variant, which was dominant when the study was conducted. But we know that the vaccines offer good protection against Delta and other variants of concern.

These results show quite clearly that vaccines offer protection for individuals who lack immunity, with important implications for finally ending this pandemic. This doesn’t change the fact that all those who can and still need to get fully vaccinated should do so as soon as possible. If you are eligible for a booster shot, that’s something to consider, too. But, if for whatever reason you haven’t gotten vaccinated just yet, perhaps these new findings will encourage you to do it now for the sake of those other people you care about. This is a chance to love your family—and love your neighbor.


[1] Association between risk of COVID-19 infection in nonimmune individuals and COVID-19 immunity in their family members. Nordström P, Ballin M, Nordström A. JAMA Intern Med. 2021 Oct 11.


COVID-19 Research (NIH)

Peter Nordström (Umeå University, Sweden)


  • PE says:

    Viruses do not, cannot replicate by themselves. So mutation is caused your own cells making transcription errors as they replicate the virus. So reducing the number of infected people also reduces the chance of a mutation.

  • Carol Liu says:

    Thank you for keeping us informed. Please continue to do so. Hopefully this will give confidence to those who are reluctant to get vaccinated.

  • CC says:

    So…..research clearly demonstrates that natural immunity exists and is highly protective. Nice to see that confirmed by the NIH. So why exactly are we forcing immune individuals in the US to take a shot or else lose their job?

  • Andrew Goldstein says:

    In addition to describing the protection from illness and death against SARS-CoV-2 from vaccines, it might help to provide some historical context about how much suffering and death vaccines have prevented from many other diseases over the last several decades. . .

    • JC says:

      I ask the same question as CC above- why is natural acquired immunity being ignored here in the US? The title of the Swedish study does not mention “vaccine-induced immunity” but “COVID-19 immunity” acquired from both vaccine and previous infection. Title of this NIH Director Blog should have been the same.

  • PTC says:

    Are there studies available that determine how long natural immunity lasts. Also, are there studies available that the vaccines offer greater immunity than persons who have natural immunity from a COVID-19 infection that was contracted 8 months ago? I think smart people with several degrees might be persuaded to get the vaccine if they have large, peer-reviewed studies pertaining to the above questions to read, rather than the possible mis-/dis-information that they might be being fed.

  • Steve White says:

    I looked at the study and found they stopped taking subjects after May 26, 2021, and then looked online to see Sweden’s number of cases had dramatically declined around that time. It is not clear if they had a Delta variant surge, or if so, when.
    After hearing about Delta variant being much more contagious, I wonder if the numbers in the study would hold up for Delta.

    I am skeptical that more exhortations, pleas, studies, or anything, will get more people to take the shots – I would like to be reading about how we are going to fend off all the variants which might arise with new vaccines. It seems almost certain part of the decline in efficacy of the vaccines is due to mutation in the virus – so, we are told this decline in efficacy is not bad enough to require new vaccines – at least implicitly we are told that, in that there is not much talk about the need for new vaccines – but do they have a handle on what may come next, new variants which escape our current vaccines completely? I do not feel confident of that. It would be nice to know it is being covered. I do not want to get political but I wish to point out, perhaps the media and government are not trusted, vis a vis the SARS2 vaccines, because of too much false information on other topics.

  • JR says:

    Notice they included PEOPLE WITH NATURAL IMMUNITY in their study. Curious and HIGHLY CONCERNING that the US public health agencies are still ignoring natural immunity. Interesting study, especially to me, as I just learned a couple of days ago that a young man I know in his late 30’s came down with a serious case of COVID-19. Last I heard he is coughing up blood, his wife has tested positive also, and his daughter who is a toddler is sick as well. Both he and his wife are fully vaccinated well before this happened. One of them got Phizer and the other Moderna. A couple in their 30’s with at least one of them SO FAR with far from “mild” symptoms. I pray they both survive.

  • Naoma quarles says:

    Yes, more people should get vaccinated but until they do, there are solutions that are cost effective and have been proven in lab tests to kill 99.9% of covid in the air inside buildings like We get covid through the air, specifically air inside buildings. Vaccines, masks, distancing, contact tracing, lockdowns-these are all defensive measures. Active Air Purification that continously treats all of the air because it operates inside the HVAC system is the only way to go

  • RM says:

    I agree it’s nice to see NIH at least acknowledge the protection natural infection provides for oneself and the community by posting this story.

    I reached out to the CDC and the VA to help understand the need for vaccination because I am hesitant myself.

    I was told I should get it for safety.

    I just had covid other month and both the CDC and VA confirmed that reinfection is RARE. They also confirmed that in the rare case of reinfection you most likely will have a mild case not requiring hospitalization.

    So essentially protection at least as good as vaccination. This study also confirms that my natural immunity protects those in my household.

    If you truly want to reach out to the people who haven’t gotten vaccinated then you need to be completely honest and explain things better. The government needs to stop holding back information it thinks will not help them get more people vaccinated. By only giving us some of the information and ignoring other evidence you create distrust.

    I for one will not get vaccinated until there is quality evidence supporting my need for vaccination and all mandates are removed. I also will only take a fully approved vaccine which provides me with legal protections. I don’t take a EUA labeled vaccine that has same formulary as an approved one. Last I checked I can’t get Comirnaty because it’s not being shipped.

    • James says:

      Although boosters have been recommended for both J&J and Moderna for susceptible people, I believe some are still EUA? There is the scientific rationale of things and then the public health facet. The latter seems to get fueled by whatever trajectory is taken in social media and other platforms that people rely on for their coverage. With respiratory viruses, there is also the aspect of mucosal immunity. Something that a natural infection is likely to do a better job of than an intra-muscular vaccine in terms of conferring an immune response.

  • Danica Delmar says:

    The study established a correlation between more people in a household being vaccinated and the likelihood of an unvaccinated family member contracting COVID. How do they know that the correlation was not due to the fact that a higher proportion of family members take the virus seriously and so are also more likely to engage in other public health measures more consistently, such as masking or social distancing. Did they control for this at all?

  • F.P. says:

    I really appreciate the findings of Mr. Peter.Me and my husband experienced it in our personal life too.

  • Lawrina says:

    Really interesting article, thank you so much

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