I’m hearing from vaccinated people who are frightened about breakthrough cases, the Delta variant, and new waves of Covid. But it’s not vaccinated people who should be most concerned. Here’s what I expect to happen over the coming weeks. 1/thread
Globally, we’re far from the end of the pandemic. Delta is at least two times more contagious than the original virus, which means it will infect and kill more people. 2/
Many countries have so far avoided big surges but haven’t had access to the vaccines needed to vaccinate their populations. Many of these countries will likely see explosive spread of Covid over the coming weeks and months. 3/
But in many places with high rates of vaccination, including much of the US, the worst is over. 4/
Though we’ll likely see big increases in US cases, future waves won’t be as deadly. That’s because 80% of the most vulnerable Americans—people over 65—are fully vaccinated. covid.cdc.gov/covid-data-tra… 5/
Fewer vulnerable people means fewer deaths. Whereas the infection fatality rate in the US before vaccines was 1 in 200, it could be less than 1 in 500, or as low as 1 in 1,000, in the coming months because of vaccine protection—even if we see many breakthrough infections. 6/
If disease continues to spread, deaths may increase, particularly among adults who are not vaccinated. Because the most vulnerable are vaccinated, the overall increase will be much smaller than past horrific increases. 7/
In the months ahead, more cases won’t correlate to more deaths in the same way as earlier in the pandemic. This graph from the UK shows why. Age matters—a lot. 8/
Vaccines will save tens of thousands of lives but are not 100%. They provide great protection, not perfect protection. More cases → more breakthrough infections. Breakthrough infections are expected, but vaccines drastically reduce risk of hospitalization & death from Covid. 9/
When infections do occur among vaccinated people, the vast majority of these cases are mild. For most, Covid is no more serious than the common cold. They’re also less likely to spread the virus, so people around them are safer, although not completely protected. 10/
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. 11/
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 with serious underlying conditions. It’s possible that the mRNA vaccines are more protective than other vaccines. 12/
Sometimes it can be hard to determine whether Covid was the true cause of death in patients receiving palliative care or already very ill, which complicates our understanding of the impact of breakthrough infections in certain groups. bit.ly/2V3yGqZ 13/
It's neither necessary nor wise for our public health systems to try to track every single mild breakthrough case. Instead, we should focus on investigating all infections as part of specific population-based studies, and also track all severe Covid illness after vaccination. 14/
When you see headlines claiming a significant proportion of hospitalized patients somewhere are fully vaccinated, don't be alarmed. Most of those stories actually underscore that vaccines are working exceptionally well against variants—including Delta. 15/
The worst is over in the US, 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 be 100,000 deaths—more, even, than from the horrific opiate epidemic. 16/
Delta is spreading. How the virus affects you when you encounter it depends on whether your body has been prepared by the vaccine to recognize and fight it—or is caught off guard. 17/
Unvaccinated people should be concerned about the rapid rise of Delta, which now makes up at least 83% of sequenced cases in the US. cbsn.ws/3rmg6Gu 18/
The more uncontrolled spread, the more risk of even more dangerous variants. Vaccination, masks, ventilation and distancing can stop Covid, including Delta. Variants remain the wild card for the trajectory of the pandemic. Delta may not be the worst strain the virus deals us. 19/
We can reduce the risk of other dangerous variants by vaccinating widely and also tamping down spread. 20/end

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More from @DrTomFrieden

23 Jul
Schools will open in weeks in the US with the Delta variant spreading rapidly. What does this mean for kids—especially those under 12 who aren’t eligible for vaccination? How can we keep them safe? These are important questions that require practical, thoughtful answers. 1/thread
The Delta variant is much more transmissible than the original virus and makes up at least 83% of sequenced cases in the US. Although most adults are now fully vaccinated, that’s not the case for adolescents, and kids under 12 can’t be vaccinated yet. 2/
Good news: Most kids who get Covid will have mild or no symptoms, and there’s no evidence that Covid caused by the Delta variant causes more severe illness among kids. 3/
Read 18 tweets
9 Jul
How big of a threat does the Delta variant pose? New developments show that the challenges we face in controlling Covid are immense. Millions of lives are at stake globally. 1/
It’s now clear that Delta spreads more readily than initial strains of Covid. It’s at least two times as infectious. bit.ly/3hLFTU0 2/
Delta may or may not be more deadly on a case-by-case basis, but because there are so many more cases, more people will get very sick, and more will die. 3/
Read 15 tweets
8 Jul
Vaccination gives you higher antibody levels and much stronger protection against Covid than natural infection, according to the best data we have today. If you recovered from Covid but still haven't been vaccinated, you may be vulnerable to reinfection—especially by Delta.
We're still learning about the duration and robustness of different types of immunity, but research suggests that people who've already had Covid are safer when they're vaccinated. Some examples:
In one study, antibody titers in people who received mRNA vaccines were up to 10 times higher than in people who recovered from natural infection. biorxiv.org/content/10.110…
Read 7 tweets
2 Jul
Vaccines Stop Cases…If They’re Given

The Delta variant poses a huge threat—but not to vaccinated people. Unvaccinated people are still being hospitalized and killed by Covid, and we’re seeing worrying Delta-fueled outbreaks, particularly in places with low vaccination rates. 1/
Don’t get caught up in fears that Delta is evading vaccine immunity. Our vaccines are working. Evidence has shown that mRNA vaccines provide excellent protection, J&J announced that their vaccine is likely also effective against Delta. bit.ly/3he9SoU 2/
Good news: Getting vaccinated virtually eliminates your risk of being hospitalized or dying from Covid. bit.ly/3jztwwT 3/
Read 11 tweets
21 May
Taming the World’s Leading Killer

An article was published this week that has findings which could save millions of lives. Why did you miss it? Because there was zero media coverage of it. Zero! Tells you something. Tells you a lot, actually. So, here are the details. 1/thread
High blood pressure is the world’s leading killer – and will kill more people, including more young people, than COVID-19 this year. It can be prevented (mostly by lowering sodium) & treated, but, globally, only 1 in 10 people with high blood pressure have it controlled. 2/
Elegant studies by @SarahLewington2 prove for every 20-point increase in blood pressure, the death rate from cardiovascular disease DOUBLES. What’s more, this starts at a blood pressure of 115/75 – way below the usual level at which we treat, or toward which we aim treatment. 3/
Read 14 tweets
18 May
Estimated excess mortality during the pandemic far outstripped officially reported Covid deaths in most countries. However, many countries, and in particular low- and middle- income countries, don’t estimate excess deaths econ.st/33VduV6 1/
Statistical modelling by @TheEconomist suggests the Covid death toll is between 7.1m and 12.7m. That means the official death toll represents, at best, about half the true toll and, at worst, a quarter of it. 2/
Most uncounted Covid deaths occurred in LMICs. In OECD countries, the true death toll was estimated to be 1.2 times the official number; in parts of Africa, it was estimated to be 14 times the official number. 3/
Read 4 tweets

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