Will the Johnson & Johnson vaccine need a second dose?

Will the Johnson &

Approved as a single dose, Janssen's Covid-19 vaccine may require a booster in the future. But the studies are still in progress

(photo: Unsplash) Safe, effective and above all single-dose. Thanks to its single administration (the way it was approved by regulatory agencies), the Johnson & Johnson (Janssen) Covid-19 vaccine has been welcomed as a crucial tool for accelerating vaccination campaigns around the world. Yet we don't necessarily need a booster in the future: studies are still ongoing.

Single-dose efficacy

Why the Johnson & Johnson vaccine was approved by agencies regulatory for single-dose use is because the clinical trials carried out have ascertained that the product confers high protection against symptomatic forms even with just one dose.

In particular, as recently confirmed in the New England Journal of Medicine, the Johnson & Johnson vaccine reaches approximately 67% efficacy in the reduction of symptomatic cases 2 weeks after administration. The effectiveness is higher in the prevention of severe and critical forms of Covid-19: 76.7% after 14 days from vaccination and 85.4% after 28 days. The percentages drop a bit in South Africa where most infections are due to the P1 variant of the coronavirus.

Ensemble 2

However, this does not mean that the studies on this vaccine are finished (but not even those on the others are finished). Even if the data acquired so far do not seem to show significant advantages in terms of efficacy with a second administration, Janssen is still carrying out a clinical trial (Ensemble 2) to ascertain this. The reason is that studies on other vaccines that use the same viral vector (adenovirus Ad26) instead show an advantage in the immune response after booster.

Ensemble 2 - reads the protocol - is a clinical study Phase 3 multicentre, randomized, double-blind and placebo-controlled phase 3 that evaluates the immunogenicity of the Ad26.CoV2.S vaccine after two doses in volunteers over 18 years living in regions at high risk of coronavirus exposure. The volunteers will be followed by the researchers for a maximum period of 2 years and 3 months.

The games, therefore, have not yet ended. "I would not put too much emphasis on the fact that Johnson & Johnson is a single-dose vaccine," Armando Genazzani, member of the Committee for Medicinal Products for Human Use (CHMP) of the European drug agency EMA, told Sky Tg24 a few days ago. "It has been studied as a single dose vaccine and we know it gives protection 14 days after administration." However, “we don't know how long it lasts. It could very well be that we need a booster later, there are studies that are evaluating it. In the meantime we can start vaccinating, though ”.


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