Personally I was keen to understand the current efficacy of the main vaccines on the market – and so went back to primary data sources to compile the below table.
|Pfizer / BioNTech (mRNA)||1st dose: 52%
2nd dose: 95%
|Moderna (mRNA)||2nd dose: 94.1%||-20°C||~$18|
|Oxford / AstraZeneca (Viral vector)||2nd dose: 70.4%||2-8°C (fridge temp)||~$2.20|
|Novavax||UK : 86%
S Africa: 60%
|2-8°C (fridge temp)||~$10|
|Johnson & Johnson||66% at 28 days||2-8°C (fridge temp)||~$10|
Data Around Efficacy Results
See BMJ article, which summarizes NEJM source. Notably 43,548 participants were randomized to 2 groups; placebo and vaccine. There were 8 cases of Covid-19 after 2nd dose in the vaccine group, versus 162 in placebo. Of the 10 total severe cases, 1 was in the vaccine group, versus 8 in the placebo group.
See NEJM article on phase 3 results. Notably, 30,420 participants were randomized to 2 groups, placebo and vaccine. There were 11 cases of Covid-19 after 2nd dose in the vaccine group, versus 185 in placebo. Of the 30 total severe cases, all were in the placebo group, with 1 death.
See Lancet article. Excuse me for interjecting a bit of editorial here, but whereas the data for the Pfizer and Moderna vaccines appears relatively simple to analyze, it’s a bit more convoluted for the Oxford vaccine. This is because the data for their 11,636 participants was split into 2 different dosage groups. The largest group (8,895 – randomized into placebo and vaccine groups) took 2 standard doses, and reported 62.1% efficacy. Whereas the smaller group (2,741 – randomized into placebo and vaccine groups) took a 1/2 dose, then a full dose, and reported 90% efficacy. They then combined the 2 results to calculate an overall efficacy of 70.4%.
Whilst it’s not impossible it’s more effective when starting with a half dose, the current plan (as I understand) is to vaccinate people using full doses. Whilst 70.4% efficacy may sound mediocre compared to the mRNA vaccines, for context the CDC reports the flu vaccine has an efficacy between 40-60%.
So far Novavax have released preliminary data from their trials – see BMJ. Quote:
“Interim results have been released from a phase III trial carried out in the UK with more than 15 000 participants aged between 18 and 84, including 27% over the age of 65. The trial tested two doses of the vaccine administered three weeks apart and reported 62 symptomatic cases of covid-19, of which 56 were in the placebo group (saline) and six in the vaccine group. Of the 62 cases, only one was severe (in the placebo group), and 32 were with the UK variant.
A phase II trial of the Novavax vaccine is also ongoing in South Africa with 4400 volunteers, in which 29 cases have been seen in the placebo group (one severe) and 15 in the vaccine group. Preliminary sequencing data of 27 of these cases found that 93% (25) involved the South Africa variant.”
Probably the most notable aspect of the results were that in the S Africa trial, 93% of the Covid positive cases were from the B.1.351 variant – which is known to have a mutation (E484K) in the spike protein that can reduce vaccine efficacy. Therefore the efficacy result of 60% is fairly reasonable.
Note: Efficacy data is likely to continue to change over time – but the above was last checked Feb 8