Herd immunity to Covid? Maybe an impossible dream. We need to reframe our approach to the pandemic and learn more, and limit the death and disruption. Here’s how. 1/thread
No one knows what will happen next in the pandemic. Longer-term predictions are just guesses. But we do know the endgame has shifted. Eradication is not possible. Even control will be difficult. We can reduce transmission and severe disease, but we can’t eliminate them. 2/
Today an FDA committee voted to recommend booster doses of Covid vaccines for people ages 65 and older and those at high risk of severe disease. Unlike Israel, they decided there is currently insufficient evidence of the need or benefit for everyone to get boosters. 3/
The situation in Israel demonstrates the challenges. Israel was an early leader in vaccinations but is now facing a big surge in Covid cases. They’ve provided a trove of important data on vaccine effectiveness, but important questions remain. 4/
Data from Israel—presented to the FDA committee today—shows that the Pfizer vaccine (the only one they’ve used) appears less protective against infection now than before. Whether that’s waning immunity or the virulence of Delta or both isn’t known with certainty. 5/
The good news is that data from Israel shows that vaccines still protect remarkably well against severe illness and death from Covid. Hospitalizations and deaths have not increased at nearly the same rate as in previous waves. 6/
One important unknown: To what extent do increasing breakthrough infections foreshadow increasing severe infections? Recent data suggest the effectiveness of Pfizer against severe disease has decreased somewhat over time among older adults during Delta. bit.ly/3Cs7BhB 7/
Does what we’re observing in Israel with the Pfizer vaccine apply to other vaccines? Not entirely clear, though the CDC data published today suggests that Moderna offers more effective and persistent protection against hospitalization than Pfizer. bit.ly/3Am7tzw 8/
Moderna uses a higher dose. It also has a 4-week not 3-week interval between doses, which probably increases efficacy. And it was approved more recently, so there’s been less time for immunity from Moderna’s vaccination to wane—if waning is a problem. 9/
If more breakthroughs are from Delta rather than waning, a dose of Delta-specific tweaked mRNA vaccines may offer better, longer-lasting protection than an additional dose of existing vaccines. But it’s not either/or. 10/
It’s crucial that we get data on risk factors for severe breakthrough. That involves transparently studying these cases to inform decisions about boosters. This is the data that scientific expert advisory groups and regulatory agencies need to make informed recommendations. 11/
Some questions the FDA committee asked:
- Whether protection against severe disease will wane in the general population
- If waning of protection is caused by time or Delta
- If boosters meaningfully strengthen protection
- Safety of boosters
- If boosters stop transmission 12/
We already know that people who are immunocompromised aren’t well protected by two doses and a third may help as part of their primary series. We may also need a different vaccine schedule or dosing for older adults. Some types of vaccines are given at 0, 1, and 6 months. 13/
Given what we know and don’t know at this point, a sensible way forward is becoming clearer based on filling our knowledge gaps, protecting the most vulnerable, and reducing the risk of new dangerous variants emerging. 14/
I agree with the FDA group that a third dose makes sense for people 65+ and at high risk. Though we aren’t certain it will be necessary or effective, it’s reasonable to conclude that it will be. Even more important is to increase vaccine uptake among these groups. 15/
We also need to consider an mRNA dose for those who initially received J&J vaccine. 16/
We MUST increase global vaccine supply through tech transfer—especially mRNA vaccines. Donations are not enough. So far, the US has failed to increase manufacturing. Neither Pfizer nor Moderna have behaved as good corporate citizens. 17/
(That’s the polite way of saying their behavior in focusing on selling boosters to rich countries and not expanding production for the rest of the world, and, in the case of Pfizer, claiming Africa can’t handle the vaccines, is egregious beyond words.) 18/
I’m disgusted by the activities of Pfizer and Moderna. I’m disappointed by the failure of the Biden Administration to scale up manufacturing. And I’m disheartened that CDC and others haven’t done better studies of risk factors for severe breakthrough. 19/
Failure to increase vaccine production is a moral failing and epidemiologically short-sighted. The US taxpayers paid for Moderna’s invention, and Moderna now has $12 billion in the bank. It’s way past time for the US to ensure Moderna shares this technology much more widely. 20/
If not:
- The US and world will be vulnerable to newer, more virulent variants that arise from uncontrolled spread
- Travel and trade will not recover
- Political instability will increase
- Millions will die unnecessarily
- The pandemic will be unnecessarily prolonged. 21/
There’s a myth there will be a vaccine glut in 2022—nonsense!
- Manufacturers missed targets by 96% in 2020
- Manufacturers (excluding China) will miss their targets by over half in 2021
- Boosters, re-vaccination, tweaked vaccines etc
- Global need >10 billion doses in 2022
22/
At current production levels, it will take YEARS to produce this. We need a step-function up, and this can only be done by stopping the current situation in which two companies hold the world hostage. 23/
We can’t rely on vaccination alone to contain Covid. Masks, testing and other measures are also necessary. But we must still increase vaccinations—our most powerful tool—around the world to prevent deaths, preserve health care, and reduce spread as much as we can. 24/
Finally, we must learn this lesson and act accordingly: Health protection and public health matter.

Microbes outnumber us, we must work together to outsmart them. 25/end

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More from @DrTomFrieden

3 Sep
Delta’s sharp rise in the UK and Israel presaged the large wave we’re facing in the US. But in key ways, our epidemic curve looks different. I’ll explain how it’s different, why, and what this tells us about the future of the pandemic. 1/thread
In the US, we haven’t tested at nearly the rate of the UK and Israel. We test at less than one third their rate of testing. Because of this, we have likely missed A LOT more cases. 2/
This may explain why our curve doesn’t go quite as high as Israel’s or the UK’s. The number of actual infections is likely much higher (at least 3X, maybe more than 5X) than the number of reported cases in the US. 3/
Read 12 tweets
14 Aug
CDC recommended today that some people with weakened immune systems get a third dose of mRNA vaccine as part of their primary series to achieve better protection from Covid. This recommendation makes sense. 1/thread
About 2.7% of US adults—roughly 7 million people—are immunocompromised, which means they have a condition that may interfere with how their body responds to infections as well as to vaccines. Here are CDC’s new recommendations: bit.ly/3CPngZ0 2/
Evidence shows that people with these conditions are at higher risk of severe illness and death from Covid, can shed virus longer and transmit it more to household contacts if they get infected, and are less protected by vaccines. 3/
Read 18 tweets
11 Aug
If the Covid surge in the US follows the pattern of the UK and India, we’ll see cases top 200,000 in the coming weeks—but we may also see a sharp and sudden decrease soon after.

Why do explosive surges caused by Delta seem to burn out so quickly? A theory...

1/thread Image
No one knows for sure why cases have plunged so precipitously in countries where the Delta variant has become dominant. But understanding this trend could help us gain control of the pandemic. 2/
There’s been a lot of focus on one epidemiological term: the basic reproductive number, or “Ro,” which is the average number of people infected by one case without vaccination or control measures. Delta is at least two times as infectious as other strains, with an Ro of 5-6. 3/
Read 23 tweets
31 Jul
Perspective: Here's the most revealing set of graphs I've seen in a long time. The UK's latest surge started about 33 days before the surge here in the US. 1/thread of 5
If the US case trend follows that of the UK, we'll have more than 200,000 cases a day by early September, possibly many more. See how the lines on the right are almost perfectly parallel. 2/5
What was somewhat reassuring is the relatively modest increase in the UK hospitalization rate. This suggests that because of the UK's very high rate of vaccination of seniors, the proportion of infections that are life-threatening is much lower. 3/5
Read 5 tweets
30 Jul
I’ve heard concern over the past few days about the impact of Delta, and questions about new guidance from the CDC. The bottom line is the virus has adapted and we must adapt too. Delta is different, but our vaccines are still doing their job. 1/thread
Earlier this week, CDC issued new guidance that everyone—vaccinated and unvaccinated​​—should wear masks indoors in areas with high rates of Covid. And last night, information was published referencing new evidence and new challenges posed by Delta. wapo.st/3lfovuy 2/
Delta is at least 2x as transmissible as the original virus, and appears to be among the more infectious viruses, estimated to spread about as readily as chickenpox. But Delta can be controlled, just as we’ve controlled chickenpox​​—through vaccination & other measures. 3/
Read 22 tweets
28 Jul
Thanks Dr. Rasmussen! Important points on the virology, but I believe the epidemiology is important also. We seem to agree there's a non-zero risk of strains emerging that aren't well protected against by current vaccines. We may disagree about how far from non-zero that risk is.
Yes, flu mutates faster—but we haven't seen two-fold changes in flu transmissibility in one season with one strain. With so much transmission, many new variants of SARS-CoV-2 are likely to continue to emerge.
There’s debate about whether vaccine-induced immunity can result in vaccine escape. As you correctly note, it’s not analogous to antibiotics, where use clearly drives resistance.
Read 8 tweets

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