The effectiveness of Johnson & Johnson and Novavax vaccines can’t be summed up in a single quantity

Novavax released its first results in a press release on Wednesday. These results have not yet been submitted for publication or peer reviewed.

In a UK study of 15,000 participants, the vaccine showed an overall effectiveness of 89.3%. At first glance, this number seems a bit lower than Moderna’s 94% and Pfizer’s 95%. In the Novavax study, however, around half of these UK participants were infected with the rapidly spreading variant B.1.1.7.

By sequencing the virus strains of infected patients, Novavax revealed an estimated efficacy of 95.6% against the original COVID-19 strain and 85.6% against the B.1.1.7 UK variant.

Novavax also reported results from a Phase 2B study in South Africa, and there the results are more complicated. The overall effectiveness in South Africa was only 49.4% – a sharp drop from the numbers seen in the UK. However, about 6% of the South African sample population were HIV positive and about a third showed SARS-CoV-2 antibodies at the start of the test, which indicates they likely had COVID-19 infection at an earlier stage. Preliminary data shows that 92.6% of those infected in the South African group had the new, rapidly spreading variant B.1.351. How all of these factors contribute to the results is not clear. Without the HIV-positive group, the vaccine was 60% effective in South Africa. This suggests that, by variant, the vaccine is 35% less effective against the B.1.351 variant than against the original virus (including the European variant that developed shortly after the virus spread from Wuhan).

In addition to the UK and South Africa studies, Novavax is conducting Phase 3 studies in both the US and South America. However, these studies began recruiting much later than Thursday and are unlikely to produce results until the end of February.

The Johnson & Johnson data are also interim results published by the company, not peer-reviewed data. These data come from a large, cross-country ENSEMBLE study that was treated as a single study when cases were aggregated based on endpoints (ie the target number of infections that will trigger the end of a study). The data were then split up again by region. Overall, 44% of Johnson & Johnson volunteers were in the US, 41% in Central and South America, and 15% in South Africa.

Johnson & Johnson reports on the effectiveness of their vaccine as 72% effective in the US, 66% in Latin America and 57% in South Africa.

However, there are some big warnings about this data. Most importantly, Johnson & Johnson reports something very different from any other vaccine company. They give an effectiveness number that represents “protection against moderate to severe COVID-19 infection”. This means that they do not include mild or asymptomatic infections in this value. This is a valid representation of the data, but differs from what other vaccine manufacturers say.

Previous results from Moderna and AstraZeneca have shown that their vaccines are also effective in preventing the spread of COVID-19. By ruling out mild or asymptomatic cases, Johnson & Johnson seems to rule out the idea that their vaccine can be effective in preventing infection.

The Johnson & Johnson numbers also represent a “time slice” of the vaccine’s effectiveness 29 days after injection. It takes time for a vaccine to take effect. However, by getting rid of infections that appeared in the first month after the vaccine was administered, Johnson & Johnson has definitely removed some cases that have been put on other manufacturers’ accounts. When the full dataset of these studies is published, expect the published numbers to look significantly different.

As with Novavax, the different efficacy figures in different regions are mainly due to the variants involved. In the results from South Africa, 95% of those infected caught them B.1.351 variant. It is not clear whether the results in Latin America include patients infected with the Brazilian P.1 line, but this could explain the lower numbers in this region, since the P.1 variant mutations share with the B.1.351 Variant.

Ignoring milder cases can make it seem like Johnson & Johnson is increasing the effectiveness of their vaccine. Even so, turning COVID-19 into a mild, cold-like disease is not an easy task, and the data contains some very good news as well.

One of the reasons the Johnson & Johnson vaccine has been monitored so closely is because it only requires a single dose. From the data from these preliminary results, it can be seen that that single shot seems to offer more and more protection over time. In fact, the number of vaccine patients infected was zero after 49 days. This isn’t a promise of perfect effectiveness for people willing to keep their masks for a few more months – after all, the majority of those involved in the study weren’t even vaccinated for 49 days when calculating this data – but there are strong signs for the vaccine to get better over time, even against the elusive variants.

Novavax is already filing for approval of its vaccine in the UK. However, don’t expect the company to seek FDA approval for the emergency until the data from the US and South America studies are back. The U.S. has already reserved 100 million doses of the Novavax vaccine, but doesn’t expect it to be available until April or May.

Johnson & Johnson is now roughly where Moderna or Pfizer were in early November. Wait another week or two for the test to reach its final endpoints. Then at least a couple of weeks for Johnson & Johnson to prepare this data for submission to the FDA. As mentioned above, the public reporting of their data is different from that of other manufacturers, and it is unclear how they organize their information for the FDA or how the panel of experts will move forward. At best, this vaccine could be available in early March.

Effectiveness of the vaccine

vaccine US United Kingdom South Africa L. America
Novavax * – – 89% 49% – –
NOT A WORD** 72% – – 57% 66%

* Trials in the US and Latin America are still ongoing

** Reports prevention of moderate and severe cases of COVID-19 only

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