Delta is dangerous and spreading -- but vaccination can stop it

enablePagination: false
maxItemsPerPage: 10
totalITemsFound:
maxPaginationLinks: 10
maxPossiblePages:
startIndex:
endIndex:

Courtesy: Jon Cherry/Getty Images

Editor's note: Dr. Tom Frieden, director of the US Centers for Disease Control and Prevention during the Obama administration -- when he oversaw responses to the H1N1 influenza, Ebola and Zika epidemics -- is President and CEO of Resolve to Save Lives, an initiative of Vital Strategies, and Senior Fellow for Global Health at the Council on Foreign Relations. Twitter: @DrTomFrieden

(CNN) — I'm hearing from vaccinated people who are frightened about breakthrough cases, the Delta variant and new waves of Covid. But people who are fully vaccinated are not the ones who should be most concerned. As new cases continue to climb almost everywhere, here's what I expect to happen over the coming weeks.

Globally, we're far from the end of the pandemic. Delta is at least two times more contagious than the original strain of the virus, which means that it will infect and kill more people.

Many countries that have avoided big surges so far don't have access to the vaccines they need to protect their populations. Many of these countries will likely see explosive spread of Covid over the coming weeks and months. Already stressed health systems will become overwhelmed with cases, and many people will get sick and die.

But in places with high rates of vaccination, including much of the United States, the worst is over. Though we'll likely also see big increases in US cases, future waves won't be as deadly. That's because 80% of the most vulnerable Americans -- people over age 65 -- are fully vaccinated.

Simply put: Fewer vulnerable people means fewer deaths. Whereas the US infection fatality rate before vaccines became available was 1 in 200, that rate could shrink to less than 1 in 500 or even as low as 1 in 1,000 in the coming months because of the strong protection provided by vaccines -- even if we see many breakthrough infections.

In places where disease continues to spread, deaths may increase, particularly among adults who are not vaccinated. Because the people most vulnerable to Covid have a high vaccination rate, the increase in deaths will be much smaller than the past horrific increases. But we have to prepare ourselves for the eventuality that more people will die -- some of whom will be young and otherwise healthy.

In the months ahead, more cases won't correlate to more deaths the same way as earlier in the pandemic. This graph from the UK shows why. Death rates have plummeted, especially among older groups, even as case rates have increased, because most of the elderly are vaccinated. But even though the rates are far lower than they were, people in all age groups are still dying.

Vaccines have saved hundreds of thousands of lives already and will save hundreds of thousands more, but they're not 100% effective. No vaccine is. They provide great protection -- not perfect protection. More cases will lead to more breakthrough infections, which is expected, but vaccines drastically reduce risk of hospitalization and death from Covid. People who are vaccinated are also less likely to spread the virus, so people around them are safer, although they aren't protected completely.

When breakthrough infections do occur among vaccinated people, the vast majority are mild. For most, Covid will be no more serious than the common cold. Unfortunately, some breakthrough infections will be less mild, requiring hospitalization and, in rare cases, resulting in death. That doesn't change the reality that vaccination is the best way to protect ourselves from Covid.

We need better data on severe breakthrough infections, but my guess is that they're more likely to occur in people of advanced age or who have serious underlying health conditions such as lung disease or immunosuppression, including immunosuppression from medications. It's possible that the mRNA vaccines are more protective against Covid than other vaccines; studies will determine whether this is the case.

It is neither necessary nor wise for our public health systems to attempt to track every single breakthrough case that causes no or only mild symptoms. There are simply going to be too many, and there is little benefit to tracking illnesses that are no worse than a cold. Instead, it makes sense -- as is being done -- to do special studies of all breakthrough infections as part of specific population-based studies, and also to try to track every severe Covid illness after vaccination. This should give us much better information about who is most at risk of serious illness from Covid after vaccination, and might lead to different dosing recommendations for some groups.

When you see headlines claiming that a significant proportion of hospitalized patients somewhere have been fully vaccinated, don't be alarmed. Most of those stories actually underscore the fact that vaccines are working exceptionally well against variants of concern, including Delta. Where most people are vaccinated, most cases will be among the vaccinated.

The worst is over in the United States, but, on average, 200-300 people are still dying every day from a disease that didn't exist 18 months ago. If that rate continues for the next 12 months, that would total 100,000 deaths -- more, even, than occur each year from diabetes or from the horrific opioid epidemic.

Delta is spreading, and in some areas is spreading rapidly. How the virus affects you when you encounter it depends on whether your body has been prepared to recognize and fight it -- or is caught off guard. People who remain unvaccinated should be especially concerned about the rapid rise of Delta, which now makes up at least 83% of sequenced cases in the United States.

The more cases there are, the more uncontrolled spread there will be, and the higher the risk that even more dangerous variants can emerge. Variants remain the wild card for the trajectory of the pandemic. Delta may not be the worst strain the virus deals us, but we can reduce the risk of other dangerous variants by vaccinating widely as well as continuing to tamp down spread. Vaccination, masks, ventilation and physical distancing can stop Covid, including Delta.

Our slow pace of vaccination has given the virus extra time to adapt and mutate, but we can wrest the advantage back by using the best weapon in our arsenal -- vaccines -- complemented by measures that slow spread of the virus including masking, ventilation and avoiding events that can amplify spread of the virus.

This story was first published on CNN.com, "Delta is dangerous and spreading -- but vaccination can stop it."