Vaccines are changing the way we interpret COVID-19 numbers


It has never been possible to know for sure how many people in the United States are sick with COVID-19 at any given time. Instead, we combine all the statistics – the percentage of tests performed that come back positive, the number of new cases reported each day, people coming sick to the emergency room with COVID-19 symptoms – to get an estimate. It’s like the story of the blind men and the elephant: experts can try out the different pieces of information to get an idea of ​​what an outbreak looks like, even if they can’t see it right away.

Over the past year we have seen the same elephant pop up over and over again. First, the percentage of tests that come back positive increases. After a short delay, hospital admissions begin to increase, and then deaths. But this time there is a new wrinkle: vaccinations. That will change the pattern and make COVID-19 trends more difficult to interpret in the coming weeks and months.

One of the most important data points to track the spread of the virus is the number of people hospitalized with a COVID-19-like illness at any given time. It is a concrete measure. If someone is so sick that they need to be hospitalized, they are usually in the hospital. Other measures, such as the number of cases and the percentage of positivity tests, are tricky; they fluctuate based on how many people decide to get tested.

“Hospital admissions are our hard outcome. Everything else is so dependent on testing, ”said Melissa McPheeters, co-director of the Center for Improving the Public’s Health through Informatics at Vanderbilt University. So we looked at hospitalization trends to get a sense of the direction of the pandemic, even as the number of cases fluctuates.

Now COVID-19 cases have occurred start to go up again in the United States. But over this time 70 percent of people over 65 in the United States have received a first dose of a COVID-19 vaccine. This is the group most likely to be hospitalized or die if they contract the virus. Now they have been vaccinated – and their risk of hospitalization and death is unbelievably small.

That could confuse our normal data patterns. Cases may be increasing as many states are relaxing restrictions while most people are still not vaccinated. But the unvaccinated people who get sick may be younger and less likely to be hospitalized.

Our normal method of visualizing the elephant would no longer work. It’s a good problem to have – fewer people in the hospital is a wonderful win. But when the number of cases wobbles and the testing goes up and down, hospital admissions will no longer be a reliable backstop to clarify what’s happening with the pandemic. “I don’t know if we can get a good example of what is happening in the community,” says McPheeters.

It may mean rethinking the way we monitor the pandemic. Perhaps fewer people will be admitted to the hospital, but we can take a closer look at that group, for example. If there are many people from a particular part of a city in the hospital, or people who work in a similar industry, that could be a signal that there is more virus in that particular community – which could help people determine their risk and show officials where to send resources. ‘It’s not just how many people, it is Who ends up in hospital, ”says McPheeters.

For the past year, people have been scrutinizing COVID-19 statistics to make decisions about how they should behave – whether to send kids to school, meet some friends, or have groceries delivered. Ultimately, as more people are vaccinated, new patterns can emerge that can guide that analysis. And when the pandemic starts to fade, we don’t need to scrutinize the COVID-19 numbers so closely. But for now everything is moving, and we cannot assume that a number means the same today as it did in January.

Here’s what else happened this week.


Unlock the Covid code
Dive deep into the world of genetic sequencing – and discover how this tool could change public health in a post-pandemic world. (Jon Gertner / The New York Times)

No one can find the animal that gave people COVID-19
Groups are looking for the animal that first passed the virus that causes COVID-19 to humans, which started the pandemic. It’s not an easy task, and international politics makes it so much more difficult. (Anthony Regalado / MIT Tech Review


AstraZeneca’s wild ride
On Monday, AstraZeneca announced that its vaccine is 79 percent effective. The next day, the government issued an incredibly unusual public rebuke against the company, saying those numbers were out of date. AstraZeneca released new numbers later this week and found that it was really 76 percent effective. Oof. Ultimately, it is a pretty good vaccine with a poor communication problem. The FDA committee hearings for this one are going to be interesting. (Nicole Wetsman / The edge

Pfizer is starting to test its vaccine in young children
Children under the age of 12 are beginning to participate in clinical trials for COVID-19 vaccines. Pfizer and Moderna are both starting their own studies to test how well the vaccines work in younger patients – and whether they are safe. (Apoorva Mandavilli / The New York Times

Here’s a great video from our colleagues at Vox explaining the differences between vaccine efficacy rates.


There were two weeks in the summer when she smelled nothing but phantom smoke. The smell was so strong that she woke up one morning, convinced that something was on fire in her house. Some time later she could smell her boyfriend’s scent again – but instead of the familiar scent she’d always loved, it was a sickening chemical scent. There’s also the hand soap at work, which smelled generically fruity to her, but now smells precisely and eerily like Burger King Whoppers.

– Sarah Zhang writes about Ruby Martinez’s experience of restoring her sense of smell after COVID-19 in The Atlantic Ocean

On December 10, my health insurance had charged me $ 536,000. My plan paid for the most, but I still owe about $ 150,000. That does not include my bill for the implant. The medical bills are lagging; it takes months for things to come through. It was stressful for me to watch it at first, but now it’s a joke. I look at it and think: I don’t know how to pay for it. My premium is $ 750 a month, and my colleagues helped cover that.

– Liza Fisher tells journalist Wudan Yan about the cost of COVID-19 in a story before Intelligencer

More than numbers

To the more than 505 million people who have been vaccinated – thank you.

To the more than 125,864,307 people worldwide who have tested positive, may your path to recovery go smoothly.

The families and friends of the 2,761,409 people who have died worldwide – 547,756 of those in the US – are not forgotten about your loved ones.

Stay safe, everyone.