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Explainer: Here's what we know about Johnson & Johnson's one-dose vaccine

The vaccine is expected to get the green light from the EU regulator on Thursday.

Image: Marta Lavandier

A COVID-19 VACCINE developed by US pharmaceutical company Janssen – owned by Johnson and Johnson – is expected to be approved next week.

The Irish government has said this one-shot vaccine will be a “big help” in the vaccine rollout, which has been slowed by delivery issues with the manufacturers of the three vaccines currently in use.

Ahead of its approval, let’s look at what we know so far about the vaccine.

Why is this one a ‘game-changer’?

The AstraZeneca vaccine was described as a game-changer before it was approved by the European regulator because it does not require the ultra-cold temperatures that the Pfizer/BioNTech and Moderna vaccines need. 

This was, however, before it became apparent that there was insufficient data at approval stage on the efficacy of the vaccine in older age groups.

European countries have taken different approaches – in Ireland the AstraZeneca vaccine is not currently being used to vaccinate the over 70s, which has meant a quick and significant shift in the health service’s rollout plan for this cohort. 

So let’s look at what benefits the Johnson and Johnson vaccine offers. Essentially it offers the ease of use and storage of the AstraZeneca vaccine coupled with robust efficacy data across all age cohorts. 

Unlike the two-dose vaccines we’re using currently, this vaccine only requires one dose. The vaccine can also be stored at fridge temperatures which opens it up to use in settings like GP surgeries, pharmacies and mass vaccination centres. 

The manufacturer has said that its large Phase 3 trial included “significant representation” from those who are over the age of 60.  The EMA, on approval of the vaccine, will provide guidance to member states on the use of this vaccine in specific age cohorts. 

What kind of vaccine is it?

The Johnson and Johnson vaccine uses viral vector technology - the same approach as the Oxford/AstraZeneca vaccine. Viral vector vaccines use a modified version of a different virus – the vector – to deliver instructions to human cells. 

The Johnson and Johnson vaccine uses a common cold-causing adenovirus which has been modified so it cannot replicate.

This ‘vector’ virus tells human cells to create the spike protein of the coronavirus. It prepares the immune system, training it to respond when it does come across SARS-CoV-2, the virus that causes Covid-19.

How effective is it?

In large clinical trials, the vaccine’s efficacy against severe disease was 85.9% in the US, 81.7% in South Africa and 87.6% in Brazil. 

Among 39,321 participants across all regions, the efficacy against severe Covid-19 was 85.4%, but it fell to 66.1% when including moderate forms of the disease.

The level of overall protection in South Africa, where another variant of the virus is circulating, dropped to 57%.

According to trial data, significant protection was reached by 29 days after the vaccine was administered. 

Analyses of different demographic groups revealed no marked differences across age, race, or people with underlying conditions.

The vaccine was generally well-tolerated, with no reports of severe allergic reactions. Mild to moderate reactions such as pain at the injection point, headache, fatigue and muscle pains were more likely to occur in younger participants. 

Where is it approved?

Last week the US Food and Drugs Administration (FDA) authorised the vaccine for  emergency use. 

Large-scale trials have also been conducted in Brazil and South Africa, but the vaccine has not been approved by regulators in these countries yet. 

When can we expect a decision from the European regulator?

The European Medicines Agency has said it will decide on whether to authorise the vaccine on 11 March. 

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This would allow the vaccine to be rolled out in early April. 

How many doses will Ireland get?

If everything with supply chains and coordination here on the ground goes to plan  Ireland should receive up to 150,000 doses of the vaccine per month in April, May and June. 

” We are hoping that Johnson & Johnson, and the vaccine that company has, will be available in April at least,” Taoiseach Micheál Martin said recently. “And that will be a big help.

“So, we will have more vaccines from March onwards until June, so a lot of people will be able to get vaccines during that period, and even more then in July and August.”

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