For about the past six months, adult Americans have had access to free vaccines that promised to reduce the risk they would contract the coronavirus and, if they did, reduce the likelihood that it would lead to serious illness or death. And, recognizing that this was a pretty good deal, most American adults have availed themselves of these vaccines.

Many of those who chose not to have paid a significant price. Since April, the Kaiser Family Foundation estimates that about 90,000 people died of covid-19, the disease caused by the virus, because they weren’t vaccinated. Thousands of others ended up in the hospital, surviving bouts with covid but at a significant cost.

This week, the Centers for Disease Control and Prevention released new data showing how much more negatively those who weren’t vaccinated were affected by the fourth surge in cases that began in late June. In every age group, those who hadn’t been vaccinated were much more likely to test positive for the virus. In older age groups, where the virus has consistently proved to be more deadly, those who were unvaccinated were much more likely to die.

We’ll get into the specific ratios between vaccinated and unvaccinated in a second. But we should first point out some of the interesting patterns.

One is that the rate of positive cases was significantly higher among younger people. That’s likely in part because of localized herd immunity effects. Over the course of the period included in the CDC’s data, the rates at which those aged 65 and over had received at least one dose of a vaccine increased from three-quarters to about 90 percent. Among the youngest age group, rates only hit 50 percent at the end of the period.

If young people are hanging out with other unvaccinated people, the likelihood that they will contract the virus would likely be higher than a group of heavily vaccinated older people who are socializing.

There’s also the issue of behavior. Polling has repeatedly shown that those who are least interested in being vaccinated are also less likely to take other preventive measures, like wearing a mask. It’s a group that broadly feels as though the virus doesn’t pose a serious threat to them or their family, perhaps increasing the odds that they would contract the virus even if no one were vaccinated.

You probably also noticed that, even among the oldest and most-vaccinated population, there was a fairly high incidence of deaths. It’s useful to remember that this is a group that has highly elevated risks of death in the first place. An official with a large public health system told me that they’d seen two covid-19 deaths of fully vaccinated individuals over the summer. One was over 95 years old. The other had recently had an organ transplant. Risk factors still matter.

Overall, the CDC reports that, in August, the unvaccinated were six times more likely to test positive for the virus than the vaccinated and 11 times as likely to die. If we look at this metric by age, it shifts. Within the youngest age group, the unvaccinated were 10 times as likely to contract the virus that month. Within the oldest group, the effects were more modest: they were three times as likely. There were (happily) too few deaths among those under age 30 to be instructive about the effects of the vaccine, but among the oldest people included in the CDC data, the vaccinated were five times less likely to die of the virus. Among those aged 30 to 49, the unvaccinated were 39 times more likely to die.

This is approximated using the weekly data the CDC provided, but it comports with the overall numbers it provided. And it reinforces the critical, central point: Getting vaccinated can save your life, regardless of how old you are.