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Novavax releases UK study preliminary results
Novavax's press release is here.  Some excerpts that I found interesting.
Quote:The first interim analysis is based on 62 cases, of which 56 cases of COVID-19 were observed in the placebo group versus 6 cases observed in the NVX-CoV2373 group, resulting in a point estimate of vaccine efficacy of 89.3% (95% CI: 75.2 – 95.4). Of the 62 cases, 61 were mild or moderate, and 1 was severe (in placebo group).

Preliminary analysis indicates that the UK variant strain that was increasingly prevalent was detected in over 50% of the PCR-confirmed symptomatic cases (32 UK variant, 24 non-variant, 6 unknown). Based on PCR performed on strains from 56 of the 62 cases, efficacy by strain was calculated to be 95.6% against the original COVID-19 strain and 85.6% against the UK variant strain [post hoc].

In the South Africa Phase 2b clinical trial, 60% efficacy (95% CI: 19.9 – 80.1) for the prevention of mild, moderate and severe COVID-19 disease was observed in the 94% of the study population that was HIV-negative. Twenty-nine cases were observed in the placebo group and 15 in the vaccine group. One severe case occurred in the placebo group and all other cases were mild or moderate. The clinical trial also achieved its primary efficacy endpoint in the overall trial population, including HIV-positive and HIV-negative subjects (efficacy of 49.4%; 95% CI: 6.1 – 72.8).

This study enrolled over 4,400 patients beginning in August 2020, with COVID-19 cases counted from September through mid-January. During this time, the triple mutant variant, which contains three critical mutations in the receptor binding domain (RBD) and multiple mutations outside the RBD, was widely circulating in South Africa. Preliminary sequencing data is available for 27 of 44 COVID-19 events; of these, 92.6% (25 out of 27 cases) were the South Africa escape variant.

Importantly in this trial, approximately 1/3 of the patients enrolled (but not included in the primary analyses described above) were seropositive, demonstrating prior COVID-19 infection at baseline. Based on temporal epidemiology data in the region, the pre-trial infections are thought to have been caused by the original COVID-19 strain (i.e., non-variant), while the subsequent infections during the study were largely variant virus. These data suggest that prior infection with COVID-19 may not completely protect against subsequent infection by the South Africa escape variant, however, vaccination with NVX-CoV2373 provided significant protection.

US Study:  NCT04611802
UK Study:  NCT04583995
South Africa Study:  NCT04533399

That doesn't seem like a lot of cases, resulting in wide range of efficacy at the 95% CI.  It does give a somewhat consistent efficacy against the "original"(??) COVID-19 strain as seen by the earlier vaccines.  This suggests that maybe Pfizer & Moderna will also drop off in effectiveness against the UK and South African strains.

For the South African strain, the efficacy has a very wide range at 95% CI, with the low end being virtually no protection.  

The last paragraph is a bit confusing to me.  Is it supposed to say that ANY of the 1/3 that were seropositive got the South African variant?  Simply because 1/3 were seropositive doesn't directly mean that any of them got COVID again.  Maybe they did or maybe they didn't.  What it does say to me is that their efficacy numbers may be overstated if 1/3 of the subjects perhaps already had significant immunity.  I would want to look at pre-trial seropositive stats for the other vaccines.

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RE: Novavax releases UK study preliminary results - by M_T - 01-30-2021, 04:31 AM

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