In the US, we're rapidly building immunity thanks to highly effective vaccines. Cases have been quickly dropping. What might we expect in the coming months?
A few tweets on how I think about our patchwork of outbreaks... 1/6
Immunity will not be spread evenly throughout the population. While we track vaccination coverage at the national or state level, infectious disease dynamics are inherently local. Pockets of unvaccinated people who have not previously been infected will exist. 2/6
These pockets with lower immunity will remain at risk for outbreaks. While populations with high immunity may no longer be at risk for large outbreaks, movement between areas (and from across the globe) will lead to regular re-introductions and onward cases. 3/6
The scale of the pandemic in the US thus changes, from when everywhere on the map was a fiery red, to smaller outbreaks. A case-based response (e.g. contact tracing, targeted antibody therapy) becomes more feasible to react to re-introductions. 4/6
Two more comments. First, the level of immunity needed during the spring/summer/fall may be different from that needed during the winter. Or for new variants. While low incidence indicates current success, we want to afford ourselves as much wiggle room as possible. 5/6
Second, while the US is breathing a sigh of relief, the rest of the world is experiencing a very different pandemic. We have an ethical imperative to further assist other countries by increasing contributions to #COVAX. This will help keep us all safer. 6/6
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Yes. A vaccinated person is less likely to transmit because they are less likely to ever be infected. At a population-level, this translates to reduced transmission. cdc.gov/mmwr/volumes/7…
2) But if a vaccinated person gets infected, are they less infectious?
This is hazier. Maybe they have lower viral load, shorter duration of infection. Maybe virus is contained to the nose only. But less infectious does not equal non-infectious.
A few replies mentioning the UK household study estimating 50% reduction in infectiousness. Studies of close contacts can provide valuable real-world evidence, and estimates from these studies will accrue over time. khub.net/documents/1359…
“Everyone believes in coordination, but no one wants to be coordinated.”
In today’s @WHO forum, Sir Michael Jacobs (@RoyalFreeNHS) with a call to action to improve collaboration for therapeutics research. 1/4
He provides a successful example of three large-scale platform trials collaborating to harmonize protocols for antithrombotics. Data are more valuable when they can be combined and compared. 2/4
He provides another example of countries having committees to prioritize new drugs for trials. Within the last few months, the committees have realized the advantage of sharing briefing documents and resources. Reduces duplication of effort and minimizes risk of omission. 3/4
The imminent FDA authorization of a vaccine for 12-15 year olds is great news, and adolescents should be able to access vaccine. But in the short term, we must also grapple with the ethics of vaccinating adolescents ahead of high-risk adults in other countries.
I had the opportunity to write a comment about findings from a large vaccination cohort study in Scotland. I use the comment to discuss some of the challenges of observational vaccine studies and the potential for lingering bias.
THREAD 1/11
Confounding is a key challenge in observational studies. One way to gain confidence in findings is to check for bias in results where we know the answer (usually, where we know there is no relationship). 2/11
.@_MiguelHernan describes using this approach in an Israeli cohort. They verified that they didn't see a protective effect of vaccines earlier than observed in randomized trials. At first they did see this, so they adjusted for more covariates. 3/11
The % vaccine breakthroughs in a population depends on:
- Vaccine efficacy
- Amt of virus circulating
- Length of time since vaccination
When you see 0.008% breakthroughs in fully vaccinated people, remember that many of these people haven't been exposed. wsj.com/articles/cdc-i…
I love to see small numbers as much as anyone, but know that numbers like this cannot be directly interpreted as a measure of vaccine efficacy (although I have a feeling they will be). We can only interpret them against a background rate in unvaccinated people.
Similarly, "most breakthroughs have been in elderly adults" should not be read as the vaccine is less effective in elderly adults. The majority of vaccinations (and the longest amount of follow-up time) have been in elderly adults. Again, we need more info to interpret.
Regarding vaccine safety, regulators are in a tough position. Transparency is a good principle. But one thing to do better is to limit the dead time between an announcement and the details of its rationale (the media briefing). Here be dragons. 1/3
The media briefing provided important context, that this is intended to be a short pause. That the aim is to increase awareness to (1) strengthen reporting and (2) make sure doctors use the correct drugs to treat this rare condition. They scheduled a rapid ACIP meeting. 2/3
In the dead time, the media scrambles for insights but everyone is short on details. Even states trying to set policy and provide vaccines don’t have all the information. So it’s a hard job, but there’s more to be done to get that important first version of the message right. 3/3