The Johnson & Johnson vaccine promises renewed optimism for widespread distribution

Written by: Parker Davis
Edited by: Esther Melamed

On Friday, January 29, Johnson & Johnson posted a press release on their website announcing the Phase 3 results of their COVID-19 vaccine candidate. The vaccine, which was developed and produced by Belgian pharmaceutical company Janssen, a subsidiary of Johnson & Johnson, was reported to be 72% effective in the United States, and 66% effective overall at preventing moderate to severe COVID-19; and it was 85% effective at preventing severe disease. The company also noted that on day 28 post-administration, the vaccine “demonstrated complete protection” against hospitalization and death due to COVID-19. In addition, the press release states that the vaccine provides protection from severe disease across all age ranges (18 and over), and from the new South African variant of SARS-CoV-2. It remains to be seen how well this vaccine – or any other currently available vaccine – protects against the other emerging strains of SARS-CoV-2.

The Johnson & Johnson vaccine is administered as a single dose (compared to the two-shot regimen of the Pfizer and Moderna vaccines), and the company reported no severe adverse reactions up to 28 days post-vaccination in their Phase 3 ENSEMBLE trial. In fact, serious adverse reactions were observed at higher rates in trial participants who received the placebo than in individuals who received the active vaccine. The hope is that a single dose will render administration much more efficient, and will encourage more individuals to receive the shot, whereas some may be put off by having to return for a second dose of the currently available Pfizer and Moderna vaccines. Indeed, the World Health Organization has stated that one-shot vaccines provide the highest rates of distribution, access, and compliance during a pandemic.

Whereas the Pfizer and Moderna vaccines use mRNA encoding the viral spike protein, the Janssen vaccine is based on the company’s proprietary AdVac platform technology, which utilizes a modified attenuated live adenovirus viral vector (Ad26.COV.S) to deliver genetic material from SARS-CoV-2. This genetic material is turned into protein by the infected cells, which is then recognized by the host’s immune system (check out the “Vaccine Technology” page on the Janssen website for neat animations of the vaccine in action). Notably, this platform has been used by Janssen in the past to create effective vaccines for Ebola, Zika, and HIV, among others. It is well known that this technology is able to induce long-lasting immunity, meaning that those who receive the vaccine will be protected against developing severe COVID-19 for months and perhaps years. Unlike the Pfizer and Moderna vaccines, which require freezing at temperatures as low as -80° C, the Janssen vaccine will remain viable for an estimated two years at -20° C and can be stored between 2-8° C for up to three months. This temperature range relieves the huge burden on mass distribution that the mRNA vaccines placed.

To many, seeing an efficacy as low as 66% and as high as 85% in some awfully specific populations may be alarming. These figures are nowhere near the high bar of efficacy that was set at 95% by the Moderna and Pfizer vaccines. Compared to those, the Janssen vaccine is good, but not great. But as several public health officials have pointed out, “good” may be “good enough.” Kizzmekia Corbett is a scientist from the NIH who worked on the Moderna vaccine, and as she put it, “Don’t let the perfect get in the way of the good enough.” In other words, even an efficacy of 66% is probably more than enough to fight the virus effectively – as long as enough people are vaccinated, that is. Corbett pointed out that 66% prevention is “darn good” for a vaccine given in just a single dose, especially for one produced in such an expedited manner. In addition to this, the Janssen vaccine is cheap and easy to manufacture in high quantities, compared to competing vaccines. And again, the hope is that the incentive of just a single shot will be enough to drive up the number of individuals willing to receive the vaccine. One important point to keep in mind is that differences in Phase 3 study design between Moderna/Pfizer and Johnson & Johnson may contribute to the vast differences in efficacy observed.

Johnson & Johnson have said that they plan to file for Emergency Use Authorization from the FDA by early February.