COVID Reinfections

Emily Oster

3 min Read Emily Oster

Emily Oster

COVID Reinfections

Emily Oster

3 min Read

The latest talk in the world of COVID is BA.5. In combination with BA.4 and BA.2.75 (which inexplicably someone gave the name “Centaurus”), these are the latest Omicron subvariants. They share many features with Omicron but have variations in their genetic code that render them distinct.

BA.5 has become the dominant variant in the U.S. (we think, based on fairly limited data). This fact implies that it must be either more transmissible than earlier variants or better able to evade existing immunity, or both. Without these features, it wouldn’t become dominant — a new dominant variant needs some advantage. Beyond the survival advantage, our (again, overall limited) evidence suggests that the variant is similar to the original Omicron (or BA.1, or BA.2) in terms of severity.

The presence of BA.5 has raised significant concerns — in some of the messages I get, I would say this borders on panic — about reinfection. Omicron in general, but perhaps the new variants even more so, show some immune evasion. We know already that COVID reinfection during the Omicron wave was much more common than during the Delta or Alpha waves. This has translated, in popular discussion, to questions like “Are we all just going to get COVID every three weeks now?” and “I heard that vaccines and prior infection do not protect you at all anymore.”

You know how we can better answer these questions? Data. Let’s go.

Can reinfections happen?

Yes.

Before getting into data, we should be clear on what we mean here. By “reinfection,” I mean a second (or more) COVID infection. A first infection after vaccination is a “breakthrough.”

Both these post-vaccine breakthrough infections and reinfections were much more common in the Omicron wave than in prior waves. The evolution of the virus meant that antibodies developed in response to earlier variants, either through vaccine or infection, provided less immediate protection. However: both vaccines and prior infections continue to provide very good protection against serious illness and death.

How common is this reinfection? It’s difficult to know for certain given the data we have. I’ll talk below about data on the protective effect of prior infection, but that’s a slightly different question. To get a vague sense of the extent of reinfection in at least one population, I surveyed all of you (newsletter readers, Instagram followers, etc).

I got over 21,000 responses. On one hand, this is a totally non-representative sample. On the other hand, it’s representative of you! The graphs below show reported infection counts — for individuals and a sample of their children — in this group.

Of course, a random sample would show up with different numbers. What I believe is useful here, though, is to illustrate the balance of one versus multiple infections. Again, this is in a select group and may leave out people who are more or less vaccinated, or with varying demographics.

About 60% of adults who responded here had had COVID at least once, but only about 6% reported having it more than once. When asked about their children under 18, about 53% of kids had had it, but only 4% more than once.

Again, I do not want to suggest these data are some kind of representative random sample. In this group, though, repeat infections have happened but they are not the mode.

How much protection is provided by prior infection/vaccination?

A somewhat terrified question I get a lot: “Am I totally unprotected even if I had COVID before?”

My sense is that some of this fear stems from the feeling that everyone has already had COVID, so all the infections we hear about must be reinfections. That’s not true, though. When we dive into the data we have, it becomes clear that prior infection does provide a lot of protection, even in the current wave.

One way to see that is using data from the U.K. and from New York State, both of which report the number of first infections and reinfections separately.

Let’s take the U.K. data first. On July 8 (the most recent fully reported day as of this writing) the U.K. Health Security Agency estimated 17,179 first infections and 4,607 reinfections, so about 21% of total infections were repeat infections. This number isn’t very meaningful on its own; to interpret it, we need to know how many people are at risk for the two categories.

Imagine that in the population, at the moment, 21% of people have had COVID sometime in the past. If we then — this week — saw that 21% of cases were reinfections, that would mean that infection this week was equally likely regardless of whether you had COVID before. This 21% of the population makes up 21% of infections.

On the other hand, if (say) 90% of people had COVID before, then the fact that only 21% of infections were among this population would suggest that prior infection is very protective. In more technical terms, it’s extremely important to pay attention to base rates.

In fact, estimates from the U.K. indicate that about 90% of the population have had at least one infection. Using an analog to a “vaccine efficacy” calculation, this would suggest that having had COVID before reduces your risk of infection by about 95%. It doesn’t reduce it to zero, but it’s a huge change. The New York data shows a similar number — about an 88% reduction in risk.

These numbers are back-of-the-envelope calculations that are subject to concerns about who has been infected before, their risk factors, and so on. But we see similar things from new published work out of Qatar. This paper used the entire population of Qatar to analyze the protection provided by prior infection and vaccination against COVID. It is important to note that the country has a very young population — only 9% of people are over 50, and 89% are expatriates from other countries.

The researchers’ key graph is below, showing protection provided by various experiences against symptomatic infection and severe infection, with BA.1 or BA.2. (This paper predates BA.5, so of course things could be slightly different now.)

Overall, the authors observe that prior infection is quite protective, and even more so with two or (better!) three vaccine doses. They estimate that prior infection plus three doses is 74% to 77% protective against symptomatic COVID, and 100% protective (again, young population) against severe infection. Of note here is also that two doses of vaccine — which at this point would have been quite far in the past — are protective against serious illness but not against symptomatic illness at all.

What I take from this is that if you have had COVID before, and especially if you’ve been fully vaccinated, you have significant protection against symptomatic COVID. It’s not 100%, but it’s really quite high.

What do we not know?

There is much we do not have detailed information about.  Based on some preliminary data out of Denmark and from our general understanding of illness, we expect reinfections to be on average less serious. (There was a preprint about the VA that suggested otherwise, but it is problematic; see discussion here.) However, this understanding is incomplete, and for questions about, for example, long COVID, we are in the dark.

We do not understand well the likely gap between COVID infections if people are reinfected. There are a lot of assumptions made that people are protected for 90 days, but there seem to be exceptions to that, although they are probably rare. We also don’t have a good sense of variation across individuals. If you haven’t gotten it yet, are you somehow magically immune? (Probably not.)

These are all questions I wish we had better data to answer, and I remain astonished that this many years into the pandemic, the U.S. still has not managed to create a better data infrastructure. For a long time I reacted to that by saying I hope they develop it soon (like here, here, and here). But at this point, I’m going to just say it’s too bad we do not have it and leave it at that.

The bottom line, with our imperfect data: Reinfection is possible, and has become more common over time. However, prior infection does provide some really substantial protection. Most infections you are hearing about are still first infections.

What should you do about this? 

There is a glass-half-full take here, which is that reinfection may be less common than you fear. But this discussion also forces the realization that reinfection is possible, and even if you had COVID before and have had all your shots, you could get it again. With this realization, we renew questions like “Should I fly now?” or “What about indoor dining?”

In the past, many of us were looking at data on case rates to inform decisions like this. I will level with you: that isn’t going to work now. The testing and surveillance situation in the U.S. is not good, and we really have no idea what case rates are. This is frustrating, but it seems to be where we are. The combination of this fact and the realization that reinfection is possible means that it may be time to make a less contingent, more permanent, set of choices.

You are now in a world where COVID is some risk more or less all the time, and you probably will not have much more than a vague sense of the size of the risk. Given that, what kind of long-term precautions do you want to take?

One category of behaviors that I think are straightforward for many people: get vaccinated and, especially if you are older and higher-risk, keep up to date on boosters. If you get COVID, stay home. Get appropriate treatment if you get sick. These actions will go a really long way toward preventing serious and life-threatening illness. Vaccinations will also lower your risk of getting COVID at all.

More complex are a set of choices about activity restrictions, masking, and testing. To some extent, your choices here can limit the risk of getting COVID, but they also entail some downsides. I’m talking about choices like indoor dining, movies, concerts, airplanes. Do you do these? And if you do these things, do you mask? How will you approach testing?

You have been thinking about these choices all along. The difference I see now is thinking about these choices as almost permanent, or at least long-term.

Not “Should I travel by plane this week, given the COVID rates?” But rather, “Am I comfortable with plane travel knowing the risk of COVID is present?”

Not “Should I wear a mask in the movie theater this week?” But rather, “Will I generally mask at the movies?”

Not “Should we rapid test before this particular gathering?” But rather, “Will we generally be rapid testing before we get together?”

I don’t imagine everyone will come down in the same way on these questions. Comfort with COVID risk differs for many reasons. But at this point I think the question you need to ask is: What behaviors am I willing to undertake long-term to avoid infection? This question is sort of a bummer, since it recognizes that there isn’t some moment when COVID will be gone, but it also lets you off the hook from re-making these choices every time.

Could things change? Of course. A new variant with a different profile or that causes more severe disease could alter our calculus. But none of the variants so far (knock on wood) have this feature. For now, make your decision once, knowing that the risk of reinfection is there but that it is perhaps lower than you feared.

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Updated CDC Guidelines for School and Child Care

NO QUARANTINES!!!

Emily Oster

Instagram

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The AAP’s guidelines recommend sleeping in the same room as your baby “ideally for the first six months.” However, the risk of SIDS is dramatically lower after four months, and the evidence in favor of the protective effect of room sharing is quite weak (both overall and even more so after four months). There is also growing evidence that infants who sleep in their own room by four months sleep better at four months, better at nine months, and even better at 30 months.

With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide

The AAP’s guidelines recommend sleeping in the same room as your baby “ideally for the first six months.” However, the risk of SIDS is dramatically lower after four months, and the evidence in favor of the protective effect of room sharing is quite weak (both overall and even more so after four months). There is also growing evidence that infants who sleep in their own room by four months sleep better at four months, better at nine months, and even better at 30 months.

With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide
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It was an absolute pleasure to be featured on the @tamronhallshow! We talked about all things data-driven parenting and, in this clip, what I call the plague of secret parenting. To balance having a career and having a family, we can’t hide the fact that we’re parents. If mothers and fathers at the top can speak more openly about child-care obligations, it will help us all set a new precedent.

Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents

It was an absolute pleasure to be featured on the @tamronhallshow! We talked about all things data-driven parenting and, in this clip, what I call the plague of secret parenting. To balance having a career and having a family, we can’t hide the fact that we’re parents. If mothers and fathers at the top can speak more openly about child-care obligations, it will help us all set a new precedent.

Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents
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Invisible labor. It’s the work — in our households especially — that has to happen but that no one sees. It’s making the doctor’s appointment, ensuring birthday cards are purchased, remembering the milk.

My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor

Invisible labor. It’s the work — in our households especially — that has to happen but that no one sees. It’s making the doctor’s appointment, ensuring birthday cards are purchased, remembering the milk.

My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor
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Prenatal vitamins 💊 If there is any product that seems designed to prey on our fears, it’s this one. You’re newly pregnant and you want to do it right. Everyone agrees you need prenatal vitamins, so you get them. But do you want to be that person who just… buys the generic prenatal vitamins?

Good news: fancier vitamins are not better.  Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough. 

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips

Prenatal vitamins 💊 If there is any product that seems designed to prey on our fears, it’s this one. You’re newly pregnant and you want to do it right. Everyone agrees you need prenatal vitamins, so you get them. But do you want to be that person who just… buys the generic prenatal vitamins?

Good news: fancier vitamins are not better. Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough.

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips
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When it comes to introducing your newborn to the world, timing matters. It’s a good idea to minimize germ exposure in the first 6-8 weeks; after that, it’s inevitable and, very likely, a good idea! This doesn’t mean you need to be trapped inside. The most significant exposure risks are from seeing other people at home — family, etc. These interactions are not infinitely risky, but they do pose more risk than a walk or a trip to the grocery store, since they involve closer interaction. Think simple and make sure everyone is washing their hands before holding the baby. 💛

#parentdata #emilyoster #newborncare #parentingadvice #parentingtips

When it comes to introducing your newborn to the world, timing matters. It’s a good idea to minimize germ exposure in the first 6-8 weeks; after that, it’s inevitable and, very likely, a good idea! This doesn’t mean you need to be trapped inside. The most significant exposure risks are from seeing other people at home — family, etc. These interactions are not infinitely risky, but they do pose more risk than a walk or a trip to the grocery store, since they involve closer interaction. Think simple and make sure everyone is washing their hands before holding the baby. 💛

#parentdata #emilyoster #newborncare #parentingadvice #parentingtips
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The first edition of Hot Flash is out now! Comment “Link” for a DM to learn more about the late-reproductive stage.

There are times when we expect hormonal shifts. Our reproductive lives are bookended by puberty and menopause. We discuss those changes often because they are definitive and dramatic — a first period is something many of us remember clearly. But between ages 13 and 53, our hormones are changing in more subtle ways. During the late-reproductive stage (in your 40s), you can expect a lot of changes in your menstrual cycle, including the length and symptoms you experience throughout. It’s an important time in our lives that is often overlooked!

🔥 Hot Flash from ParentData is a weekly newsletter on navigating your health and hormones in the post-reproductive years. Written by Dr. Gillian Goddard, Hot Flash provides all of the information you need to have a productive, evidence-based conversation about hormonal health with your doctor.

#emilyoster #parentdata #hotflash #perimenopause #womenshealth

The first edition of Hot Flash is out now! Comment “Link” for a DM to learn more about the late-reproductive stage.

There are times when we expect hormonal shifts. Our reproductive lives are bookended by puberty and menopause. We discuss those changes often because they are definitive and dramatic — a first period is something many of us remember clearly. But between ages 13 and 53, our hormones are changing in more subtle ways. During the late-reproductive stage (in your 40s), you can expect a lot of changes in your menstrual cycle, including the length and symptoms you experience throughout. It’s an important time in our lives that is often overlooked!

🔥 Hot Flash from ParentData is a weekly newsletter on navigating your health and hormones in the post-reproductive years. Written by Dr. Gillian Goddard, Hot Flash provides all of the information you need to have a productive, evidence-based conversation about hormonal health with your doctor.

#emilyoster #parentdata #hotflash #perimenopause #womenshealth
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There are plenty of reels telling you how to parent. Plenty of panic headlines saying that “studies show” what’s best for your kid. Even good data, from a trusted source, can send us into a spiral of comparison. But I want you to remember that no one knows your kid better than you. It’s important to absorb the research, but only you will know the approach that works best for you and your child. 💙

Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata

There are plenty of reels telling you how to parent. Plenty of panic headlines saying that “studies show” what’s best for your kid. Even good data, from a trusted source, can send us into a spiral of comparison. But I want you to remember that no one knows your kid better than you. It’s important to absorb the research, but only you will know the approach that works best for you and your child. 💙

Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata
...

Let’s talk about sex (after) baby! Today on the podcast, I was lucky enough to speak with @enagoski about her new book on sexual connection in long-term relationships. Especially after having kids, this is something many people struggle with. Emily tells us to stop worrying about what’s “normal” and focus on pleasure in its many forms.

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships

Let’s talk about sex (after) baby! Today on the podcast, I was lucky enough to speak with @enagoski about her new book on sexual connection in long-term relationships. Especially after having kids, this is something many people struggle with. Emily tells us to stop worrying about what’s “normal” and focus on pleasure in its many forms.

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships
...

Ever wondered if you can safely use leftover baby formula? 🍼 The CDC says to throw out unused formula immediately because of the risk of bacterial growth. However, research suggests that bacterial concentrations do not appreciably increase after 3, 12, or even 24 hours at refrigerator temperatures. Good news! This means there’s not a strong data-based reason to throw out formula right away if you store it in the fridge.

Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles

Ever wondered if you can safely use leftover baby formula? 🍼 The CDC says to throw out unused formula immediately because of the risk of bacterial growth. However, research suggests that bacterial concentrations do not appreciably increase after 3, 12, or even 24 hours at refrigerator temperatures. Good news! This means there’s not a strong data-based reason to throw out formula right away if you store it in the fridge.

Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles
...

What’s the most important piece of advice for new parents? Here’s one answer, but I want to hear from you! Share your suggestions in the comments ⬇️

#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity

What’s the most important piece of advice for new parents? Here’s one answer, but I want to hear from you! Share your suggestions in the comments ⬇️

#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity
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What's in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you.

What`s in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you. ...

Comment ”link” for a DM to learn more about tongue ties 🔗

Breastfeeding is often difficult, especially at the start. For babies with tongue ties, many infants (and their moms) struggle to get the hang of a good latch. This can lead to painful nipples and to inefficient feeding, and then low weight gain.

So what does the data say about the increasingly common practice of cutting tongue-ties in infants to improve breastfeeding success? Several weeks ago, @nytimes published a long and quite scary article on this topic.

After diving into the data, here is what I found. There is limited evidence that frenotomy procedures improve breastfeeding efficacy and the harms of the procedure are minimal. Many women do report that it alleviates pain and helps them with breastfeeding. However, it should not be a first-line treatment for breastfeeding problems.

#parentdata #emilyoster #tonguetie #tonguetiebabies #breastfeedingsupport

Comment ”link” for a DM to learn more about tongue ties 🔗

Breastfeeding is often difficult, especially at the start. For babies with tongue ties, many infants (and their moms) struggle to get the hang of a good latch. This can lead to painful nipples and to inefficient feeding, and then low weight gain.

So what does the data say about the increasingly common practice of cutting tongue-ties in infants to improve breastfeeding success? Several weeks ago, @nytimes published a long and quite scary article on this topic.

After diving into the data, here is what I found. There is limited evidence that frenotomy procedures improve breastfeeding efficacy and the harms of the procedure are minimal. Many women do report that it alleviates pain and helps them with breastfeeding. However, it should not be a first-line treatment for breastfeeding problems.

#parentdata #emilyoster #tonguetie #tonguetiebabies #breastfeedingsupport
...

Tag a friend who needs to hear this 💛 For many choices in parenting, there is no one right answer. We can use research and data to make informed decisions, but ultimately, it won’t tell you what to do. Only you can decide what will be best for your kids and your family.

I’m here to remind you to take a deep breath and trust yourself. I’ll be here to support you along the way. 

Thank you to everyone who submitted videos, including:
@sarah.consoli
@jess_lynn627
@nicolevandenwills
@thedrblair
@ncbenedict29
@haleycimini
@iamkellysnodgrass
@calesse_smith
@garnet__gordon
@jencoopgaiser87
@danigirl18c
@jamielundergreen
@carly_comber
@thecelebratingmama
@emilyannbynum
@eeliz413

#emilyoster #parentdata #parentingadvice #parentingsupport #parentingquotes

Tag a friend who needs to hear this 💛 For many choices in parenting, there is no one right answer. We can use research and data to make informed decisions, but ultimately, it won’t tell you what to do. Only you can decide what will be best for your kids and your family.

I’m here to remind you to take a deep breath and trust yourself. I’ll be here to support you along the way.

Thank you to everyone who submitted videos, including:
@sarah.consoli
@jess_lynn627
@nicolevandenwills
@thedrblair
@ncbenedict29
@haleycimini
@iamkellysnodgrass
@calesse_smith
@garnet__gordon
@jencoopgaiser87
@danigirl18c
@jamielundergreen
@carly_comber
@thecelebratingmama
@emilyannbynum
@eeliz413

#emilyoster #parentdata #parentingadvice #parentingsupport #parentingquotes
...

Congratulations on making it through another year of panic headlines! We’ve had some doozies this year, like aspartame causing cancer and the perils of white noise, but these headlines are very often based on poor data. Correlation does not equal causation. There will certainly be more panic headlines in 2024, but ParentData is here to debunk them for you.

#emilyoster #parentdata #happynewyear2024 #panicheadline #datadriven

Congratulations on making it through another year of panic headlines! We’ve had some doozies this year, like aspartame causing cancer and the perils of white noise, but these headlines are very often based on poor data. Correlation does not equal causation. There will certainly be more panic headlines in 2024, but ParentData is here to debunk them for you.

#emilyoster #parentdata #happynewyear2024 #panicheadline #datadriven
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