Vaccines, Kids & A Refresher on the Five Step Decision System

The melt is ... slow

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This last week has been a bit of a mish-mash for me. On the one hand, the energy of the new administration, the refocus on science has left me feeling hopeful. The fact that higher-risk members of my family are starting to get vaccinated is just awesome. At the same time, there are moments it just feels like this will never end. It’s petty, but I miss traveling so, so much. I know I’m lucky — so lucky — but there are definitely moments where it is hard to see that.

Also, the other night I had a dream that I had a positive COVID test but then they told me it was a false positive because I was eating too much lettuce. What does that even mean?

I mention this because in a way it relates to the topic of today’s newsletter: more stuff about vaccines. I’ve been getting a lot of questions. Nearly all of them are of the form: When will it be enough? When will we get to herd immunity? What about kids — it seems like they will not be vaccinated until the fall — does this mean we can’t do anything until then?

A lot of these questions stem, in my view, from poor communications (I’ll take some blame here like everyone else). We’ve been hearing the message “Even when you’re vaccinated, don’t go crazy” and interpreting it as “The vaccine will not be enough for a return to normalcy” or “We cannot return to anything closer to normalcy until everyone in the country is vaccinated.” Neither of these is true.

To see why, I want to talk through first a bit on herd immunity and how we think about policy around vaccines. Then I want to dig into how vaccines might change your family behavior — including the issues around kids. I’ll come back at the end to why understanding this is so important.

Quick note: when I say “vaccinated” here, I mean fully vaccinated. Two doses + at least a week or so after second dose for it to sink in.

Vaccines & Herd Immunity By the Numbers

I want to start by establishing two points.

  1. COVID-19 vaccines prevent any disease with very high probability and serious disease almost completely.

  2. Being vaccinated for COVID-19 lowers your risk of spreading the virus to others.

The first of these I think is clear to most people. The second has gotten a bit flubbled in the telling. Part of the reason is we do not (yet) know by vaccination decreases the risk of getting infected. Vaccines prevent disease by priming your body to fight disease when it arrives, so it is possible that people who are vaccinated for COVID-19 could still get infected, just not get sick.

However, despite this uncertainty the second point above is true for two reasons. First, based on what we know about other vaccines it seems extremely likely that the vaccine prevents infection to some extent. But, second, even if that isn’t the case, the vaccine prevents symptoms. Asymptomatic people transmit perhaps 75 or 80% less than symptomatic people. This means even if the vaccine had no effect on infection (again, really unlikely) it would lower transmission to others by 75 to 80%.

The risk of transmission from vaccinated people probably isn’t zero, and we certainly do not have the data yet to put a precise number on it, but it’s a LOT LOWER than if you are not vaccinated.

Given these two points, we can start to see what’s happening as we vaccinate people.

Let’s imagine we have 100 people, and over each time period (say, a day or a week) each person interacts with 10 other people. Now introduce someone with COVID-19, and imagine we have no vaccines. Given their interaction pattern, we’d expect this person to infect perhaps 1.5 other people. Then, those people infect an average of 1.5 other people, and so on. Pretty soon, everyone has the virus. And perhaps 5 or 6 people are hospitalized, and one dies.

That’s the no-vaccine extreme. The other extreme is the “everyone-is-vaccinated” case. There, even if someone shows up with COVID-19, we’ll never see it. It doesn’t matter how much they transmit, since no one will get seriously ill. We all agree that’s a good case, but we are far, far from this.

But, in fact, even partial vaccination is really really valuable.

Think about a case where 40% of the population is vaccinated and imagine that their risk of transmission is reduced by 80%. Note that this is actually quite conservative, since it basically assumes they are equally likely to be infected, but are just not symptomatic. In this case, when infection is introduced to the population, rather than each infected person infecting 1.5 people on average, they each infect only 1.02 person on average (since the vaccinated people transmit at a lower rate). This means the virus will not grow nearly as quickly.

And that’s just what happens if we vaccinate 40% of people at random. Now imagine we vaccinate 40% of people focusing on those most likely to get sick and those who interact with the most other people. By vaccinating the second group, we lower transmission even more. By vaccinating the first group, we see decreases in hospitalization and death.

Given the huge variation in serious illness risk across groups, even a relatively limited amount of vaccination can start to make a difference in hospitalization and death. (Case in point: 40% of COVID-19 deaths have been in nursing homes, and long term care facilities, and these house less than 1% of the US population. So vaccinating even that tiny group would potentially matter a lot for death rates).

Bottom line: as we get to 10, 20, 50 percent vaccinated, we are moving towards a situation where disease rates are likely to be much, much lower and where those who do get infected are much, much less likely to be seriously ill. Basically, rather than seeing high hospitalization rates and new deaths every day, we’ll see some milder infection continue to circulate in lower risk groups. But at lower rates. And with much less severe consequences.

In this context, we can think about the questions around children. Kids are much less likely to get infected and less likely to get serious illness even if they are infected. It’s true that it will be a long time before they are vaccinated, but the combination of overall lower infection rates will help them. And given their extremely low risk, it is going to make sense to reopen more things even if there is a chance that kids will get COVID-19.

Consider, schools (yes, I know, I’m one note). I’ve started to see some murmurings about not going back to school until all kids are vaccinated. This would be terrible policy. I think schools should try to open now. But certainly at a point where teachers plus any other high risk family members are vaccinated, the risks to having kids at school are extremely small. Will they still have to wear masks? I think this is unclear. My guess is no, but it’s hard to predict.

All this is to say: from a societal standpoint, we do not need 100% vaccination to start returning toward normal. This will come in pieces. We’re going to need higher vaccination rates to start having, say, large indoor concerts with alcohol consumption.

Personal Choices

The basics of herd immunity are good background here, but most of the questions I get are fairly specific: should I change how I think about grandparents or child care or even — gasp! — summer vacation. For many families in situations like mine, we’re facing a slow roll of vaccinations. Fingers crossed that the grandparents will be vaccinated in the next couple of months and there is perhaps some chance that by the summer the lower risk adults will be. But kids are going to wait until the fall for sure, if not later. So, how to think about it?

To do this, I want to step back to the very first Grandparents & Day Care post I put together in May. Remember the 5 step decision process? It’s still relevant here. Frame the question, mitigate risk, evaluate risk, evaluate benefits, decide.

Consider the first question: seeing the grandparents, and now let’s imagine that they are vaccinated but none of the rest of you are. The question is now likely something like “Should we see them now or wait until more of us are vaccinated?” Your options to mitigate risk are similar to before — indoor visits riskier than outdoor visits, hand washing and possibly mask wearing are important, etc.

What has really changed is the evaluate risk stage. In that original post I tried to put together some numbers on the size of risks and argued, basically, the big risks in this equation were to the grandparents. COVID-19 is most serious for older people. Putting exact numbers on it is difficult, but a November piece in Nature estimated the case fatality rates by age. They were 1 in 100,000 for kids aged 5 to 9, about 1 in 10,000 for people in their 30s and 40s, versus about 1 in 10 for people over 80. All of the adult fatality rates are variable with other comorbidities; if you are healthy to begin with, they are lower.

All of this is to say that when we thought about this decision before vaccines, the risk evaluation was heavily weighted towards the possible really, really bad outcome of your 85 year old father getting COVID. If that is effectively eliminated, it dramatically lowers the risks.

On top of this, as noted above, once the grandparents are vaccinated they are less likely to spread the disease. This means the chance of spread at the visit is correspondingly lower.

This personal risk calculation is going to continue to change as more people are vaccinated in the group. Once everyone over the age of, say, 20 is vaccinated you’re down to some very, very low risks. Could you think about traveling over the summer, even if the kids are not yet vaccinated? I do not think it is a crazy idea. Is the risk of them getting infected literally zero? No, of course not. But its a very, very small number, multiplied by the also very, very small chance of serious illness.

To go to the extreme: consider a family with low-risk children (if your child is high-risk, this calculus is more complicated). If kids are the only unvaccinated ones, you now are facing a world where there is a disease with a small risk of making your child mildly ill. Pre-COVID, you already lived in that world — there are many diseases which your child is at higher risk for and would make them sicker than COVID-19. Considering only your family, there is a case for returning to normal.

The five step decision process doesn’t make the decision for you, and it’s very personal. There’s also the benefits to consider. Some people may decide, for various reasons, they still feel the risk is too high or the benefits to doing various things seem small. Waiting until everyone is vaccinated is a choice some may make.

But there is no question the risks associated with this activity are much, much lower once some high-risk members have been vaccinated. So reasonable people who avoided seeing family before may well — rationally — decide to see them now.

The Bigger Picture

David Leonhardt wrote last week about our “underselling” of vaccines. His point was that by emphasizing they may not literally prevent all spread, we lead people to think vaccines are less good than they are. This seems important to me, although at this point our barriers to vaccination are mostly supply and not demand.

A related issue with underselling is we limit hope. This gets back a bit to the top of my post. Mental health issues are real; people are really, really struggling. Sending the message that it will always be like this not matter what and you can never see your grandchildren again is damaging.

My sense, though, is that the biggest danger here is that we set incorrect expectations. I fear that, at times, we’re moving toward messaging like “We can reopen when there is no more COVID-19.” This is, quite possibly, never. We can imagine getting to a place with very little serious illness and very little spread, but even with great vaccines we still see some measles and pertussis. And we should expect some coronavirus in circulation also.

To be clear, I’m not pushing something like the Great Barrington Declaration, suggesting we reopen with abandon and just let COVID ride. But there is a big gap between that and saying we can start seeing our families a bit more after the high-risk populations are vaccinated. We already take some risks — we drive cars and ride bikes and go out during flu season — without thinking about them too much. There is a delicate balance here, since for many reasons it would be a mistake to suggest that once you’re vaccinated you can just do whatever you want.

But I think it’s also a mistake — both personally and as a society — to go too much in the other direction. We need to learn to think about this risk rationally in both directions. There is too much COVID denial out there — see this second Leonhardt piece about lack of mask wearing. But also, sometime, not enough recognition of the hope and the ways our behavior can safely change as the vaccine rolls out.


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