The Oxford trial (for all its sins) did serial PCR tests on all its participants. So of the three vaccines in the headlines recently it’s the only one that will generate data on any potential reduction in asymptomatic carriers.
Yeah definitely a bonus for them! Shame they've not released the specific results on that yet, like all the rest of it. You'd think if they were positive they might've slipped out some findings on that by now! How much asymptomatic transmission actually takes place anyway? I thought it was fairly low.
Sorry to lean on everyone here for updates but can anyone summarise why I'm hearing a bit of controversy over the Oxford vaccine's results?
It's a combination of communicating the results
poorly, giving out 1 1/2 doses instead of 2 doses accidentally (which the CEO called "
serendipity") and upon discovering that their accidental dosage worked better, not having a good explanation for why that is. And upon further investigation, it was noted that their two sets of results - one 90% effective, one 62% effective - were not only done in different countries among different groups of people, but it excluded those over 55 - and it was the
head of Operation Warp Speed that had to point that out, rather than AZ themselves.
Still a lot to learn by the sounds of it.
Sort of. Ultimately they have learned the most important part - if their analysis holds true.
This was the FDA's guidelines about efficacy:
As it is possible that a COVID-19 vaccine might be much more effective in preventing severe versus mild COVID-19, sponsors should consider powering efficacy trials for formal hypothesis testing on a severe COVID-19 endpoint. Regardless, severe COVID-19 should be evaluated as a secondary endpoint (with or without formal hypothesis testing) if not evaluated as a primary endpoint.
FDA recommends that severe COVID-19 be defined as virologically confirmed SARSCoV-2 infection with any of the following:
- Clinical signs at rest indicative of severe systemic illness (respiratory rate ≥ 30 per minute, heart rate ≥ 125 per minute, SpO2 ≤ 93% on room air at sea level or PaO2/FiO2 < 300 mm Hg)
- Respiratory failure (defined as needing high-flow oxygen, noninvasive ventilation, mechanical ventilation or ECMO)
- Evidence of shock (SBP < 90 mm Hg, DBP < 60 mm Hg, or requiring vasopressors)
- Significant acute renal, hepatic, or neurologic dysfunction
- Admission to an ICU
- Death
SARS-CoV-2 infection (whether or not symptomatic) should be evaluated as a secondary or exploratory endpoint, if not evaluated as a primary endpoint.
It's not that unusual for a vaccine to be better at preventing severe vs. mild symptoms, and if the covid vaccines that are developed were only successful at preventing severe symptoms, doing that 90% of the time would still be a big win. What we know so far suggests Pfizer and Moderna's are also successful at preventing mild symptoms, so we might go one step futher. If it was able to limit infection altogether it would be a home run really. We shouldn't be expecting that. So any more news we're expecting is just the cherry on top, if the FDA reviews the data and verifies it is effective at preventing severe symptoms.