When American experts first started to worry that COVID-19 vaccines weren’t working quite as well against delta as they did against earlier coronavirus strains, they didn’t have much domestic data to go on. The Centers for Disease Control and Prevention was only collecting data on post-vaccination COVID-19 cases if they led to hospitalization or death — the agency wasn’t doing big-picture tracking of COVID-19 in vaccinated people. Only a few states and counties were collecting and publicizing that information. 

The CDC was doing some analysis, but it wasn’t sharing the information quickly, frustrating experts who hoped for a more dynamic picture of how the delta variant was affecting vaccinated people. The agency finally released some data this week as part of the justification for pushing booster doses of the COVID-19 vaccine, but the scope was still limited and came too late. 

“It’s not acceptable how long it takes for this data to be made available,” a senior CDC official told The Washington Post. For the most part, US experts had to rely on vaccine data from other countries: Israel, Canada, the United Kingdom. 

Data, or lack thereof, has been one of the biggest challenges in the US COVID-19 response. From the early days of the outbreak, health departments have struggled to collect information on cases, and often only had delayed and incomplete data. Most clinical trials investigating COVID-19 treatments were small and couldn’t deliver conclusive answers. 

Part of the problem was that the US has a fragmented public health system, and data is siloed off in individual hospitals. Places with national health systems, like the UK, were in a better position to understand big-picture trends through the pandemic — its National Health Service was able to run a multisite clinical trial to look at COVID-19 treatments, which eventually identified treatments that saved lives. 

Over 18 months later, the problems in the US persist. Officials don’t have a good grasp on where and how COVID-19 is spreading in certain groups, former Food and Drug Administration Commissioner Scott Gottlieb outlined on Twitter. The CDC isn’t equipped to collect real-time data, he notes. That constrains the country’s response. 

Now, those problems are making it harder to understand the dynamics of coronavirus infections from the delta variant in vaccinated people in the US. Delta has only been the dominant coronavirus variant in the US for around two months, so it could take some time for the patterns to emerge. But officials are moving forward with booster plans based only on the limited information they have now. Hopefully, the data will eventually catch up with their actions. 

Here’s what else happened this week. 

Research

U.S. officials’ decision on Covid-19 booster shots baffles — and upsets — some scientists
Many experts say that the available data on vaccine efficacy doesn’t support the decision to offer boosters to everyone. The shots still hold strong against severe disease. (Helen Branswell / Stat News)

Babies and Toddlers Spread Virus in Homes More Easily Than Teens, Study Finds
Young children, who can’t be isolated when they’re sick, are more likely to pass COVID-19 onto other people living in their household. (Emily Anthes / The New York Times)

Delta’s rise is fuelled by rampant spread from people who feel fine
The virus starts building up around two days before people start showing symptoms of COVID-19. Most infections happen in the pre-symptomatic phase, making it harder to stop the spread. (Smriti Mallapaty / Nature)

Development 

COVID-19 booster shots will be offered to Americans in September, Biden administration says
Pending FDA and CDC sign-off, federal officials plan to start offering boosters to healthcare workers, nursing home residents, and others who were the earliest to get initial shots. (Nicole Wetsman / The Verge)

What’s safe to do during summer’s Covid surge? STAT asked public health experts about their own plans
Most experts surveyed say they won’t go to a movie or eat indoors at a restaurant, but they would get their hair cut — while wearing a mask. (Helen Branswell / Stat News)

A grim warning from Israel: Vaccination blunts, but does not defeat Delta
Vaccines are still working in Israel, but the number of vaccinated people who have severe cases of COVID-19 is raising concerns about waning protection in vulnerable populations. (Meredith Wadman / Science)

Perspectives 

“When they started talking about covid coming out I was like, ‘All right, we’re gonna create a vaccine, there’s gonna be a big demand for it, and Montana doesn’t have a lot of access...I hate to say it, but I literally took advantage of covid-19 to open up and push forward.”

— Kyle Austin, a traveling pharmacist, is the only person offering the Pfizer / BioNTech COVID-19 vaccine in some parts of Montana. 

More than numbers

To the people who have received the 4.5 billion vaccine doses distributed so far — thank you.

To the more than 209,804,195 people worldwide who have tested positive, may your road to recovery be smooth.

To the families and friends of the more than 4,400,048 people who have died worldwide — 624,832 of those in the US — your loved ones are not forgotten.

Stay safe, everyone.