By Public Health – Seattle & King County
Since July, COVID-19 cases have increased rapidly in King County. The worsening outbreak is affecting all of us. And, people who are not fully vaccinated are getting seriously ill and dying at much higher rates than the vaccinated population.
No vaccine is 100% protective. When a vaccinated person does become infected, we call it a “breakthrough” case. When we have more breakthrough cases that does not mean the vaccines are falling short. It just reflects that a higher percentage of the population is already vaccinated.
Most breakthrough cases are not serious. What is important to know is how much the vaccine reduces a person’s risk of coming down with a severe infection.
Public Health – Seattle & King County created the new dashboard so that anyone can track and compare the rates of cases, hospitalizations, and deaths among unvaccinated and vaccinated people. With weekly updates, it will provide a snapshot of COVID-19 risks for unvaccinated residents compared with vaccinated residents.
Why relative risk matters
Relative risk means we compare the risks for COVID-19 infection, hospitalization, and death in unvaccinated people relative to vaccinated people.
The boxes in the dashboard’s top line show the relative risk of infection (positive test), hospitalization, and death for unvaccinated people, compared with those who are fully vaccinated. For example, in the month leading up to Aug. 26, unvaccinated people in King County were:
• 7 times more likely to test positive for COVID-19 than vaccinated people
• 47 times more likely to be hospitalized than vaccinated people
• 32 times more likely to die from COVID-19 than vaccinated people
These three boxes show how relative risk for infection, hospitalization, and deaths is much higher for unvaccinated people.
We look at relative risk because the number of people who are vaccinated is not the same as the number who are not fully vaccinated. The two groups are not the same size, so a raw count or percentage of breakthrough cases doesn’t tell us much about how one group’s risk compares with the other. By comparing the rates among vaccinated people with the rates among unvaccinated people, we see that the risks from COVID-19 are far higher if you are not fully vaccinated.
With more than two-thirds of King County’s population fully vaccinated, breakthrough infections are expected. But the dashboard shows the risk of developing COVID-19 infection, especially a severe COVID-19 infection, is much higher for unvaccinated people.
Why we are “adjusting for age”
The best way to understand how well the vaccines are protecting us is to look at “age-adjusted relative risk.” This means comparing vaccinated and unvaccinated people of the same age and seeing how their outcomes differ.
For example: To get a true picture of a person’s risk, you would want to compare a vaccinated 85-year old to an unvaccinated 85-year-old. But don’t compare the 85-year-old to an unvaccinated teenager.
This matters because older age groups have higher rates of vaccination, which protects them, and also higher rates of preexisting conditions and other factors that put them at risk for more serious outcomes from COVID-19.
Compare vaccinated people to unvaccinated people, adjust for age, and then we see that vaccinated people are much better protected from getting severely ill or dying from COVID-19. The vaccines are working.
Rate over time
The current surge has driven COVID-19 transmission to some of the highest levels we’ve seen during the pandemic. However, this latest wave of infections looks very different for the vaccinated population, compared with residents who are not fully vaccinated.
The “Rate over time” graphs show that difference starkly.
This line graph shows sharply increasing case rates among unvaccinated people, and much lower rates among vaccinated people.
These graphs show how much faster the virus is spreading among unvaccinated people, compared with vaccinated people of the same age. On July 1, the case rate among unvaccinated people was about 8 cases per 100,000 people per day, while among the vaccinated it was less than 1 case. Over the next two months, cases spiked among unvaccinated people, increasing by an additional 82 cases per 100,000 people, per day. Cases rose among vaccinated people, too, but much more gently: By late August, the rate went up by just 8 additional cases per 100,000, per day.
The difference in risk is even more striking when you look at hospitalizations. Among vaccinated people, the age-adjusted rate has barely budged, up to just 0.1 hospitalizations per 100,000 people per day. Among people who are not vaccinated, hospitalizations have increased almost ninefold, up to about 8 per 100,000 per day. COVID-19 deaths show a similar trend, with vaccinated people at dramatically lower risk than unvaccinated people.
This line graph shows sharply increasing hospitalization rates among unvaccinated people, and much lower rates among vaccinated people.
With disease transmission high and more than two-thirds of King County’s total population fully vaccinated, we should expect to see even some vaccinated people get sick and, rarely, be hospitalized or die from COVID-19. But as the graphs plainly show, unvaccinated residents are at much higher risk for the worst outcomes of COVID-19.
Demographics and geography
You also can see the more specific relative risk in your own community by geographic region, by race/ethnicity, or by sex. In this section of the dashboard, you also can toggle among “cases,” “hospitalizations” and “deaths.”
In every region and in each race/ethnicity group, the risk of being hospitalized is much higher for people who are not fully vaccinated.
The contrast is stronger in communities where more people face barriers to both vaccination and basic protective measures. The barriers include racism, inequitable access to testing and vaccination, workplace conditions, and/or access to sick leave or health benefits.
The Geography and Demography sections use age-adjusted, cumulative data since January 17, 2021.
What to take away
Getting vaccinated is the best way to reduce your risk of getting seriously ill or dying from COVID-19. It’s the best way to protect yourself from getting so sick that you need to be hospitalized. And it significantly reduces your risk of catching COVID-19 at all and spreading it to others.
The transparent, regularly updated local data in the new dashboard reinforces that even during a COVID-19 surge, the vaccines are protecting vaccinated people from serious disease.
It also reminds us that no vaccine is 100-percent effective, so it is not surprising that there are still cases, hospitalizations, and even deaths among fully vaccinated people. That means we need everyone to take precautions and help stop the current outbreak from growing and potentially overwhelming our healthcare system.
In addition to getting vaccinated, you can help prevent COVID-19 from spreading by: Wearing a well-made, snug-fitting face covering in indoor public spaces and in outdoor settings where you can’t physically distance (including all large events); improving indoor airflow and ventilation; and, if you feel sick or have had close contact with someone with COVID-19, getting tested and isolating yourself while you await results. Employers can also help by providing and encouraging use of paid sick leave, so employees can get vaccinated and stay home when needed.