Johnson & Johnson vaccine Q&A: Is this the game-changer?

Approval by the European Medicines Agency of the Johnson & Johnson Covid-19 vaccine means that in a matter of weeks, four vaccines will be in use in Ireland.

The ability of all four to counter serious illness, hospitalisations and death arising from coronavirus appears to be impressive but the capacity to deliver promised supplies is a lot more problematic.

Wealthy countries, notably the UK, the US and some EU members, continue to squabble and deny they are engaging in “vaccine nationalism”. The row is compounded by some orders being fulfilled, while others are delayed.

Does the Johnson & Johnson vaccine deserve its billing as a game-changer?
To a large extent, yes. The ease of administering the vaccine, which requires a single dose that can be stored in an ordinary fridge, stands out.

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Its versatility means it can be easily deployed in challenging circumstances such as care homes and in rural areas, rather than specialised clinics or GP surgeries. In the developing world, the advantages are even more pronounced with the ability to reach remote locations and dispersed populations.

Notwithstanding the global scramble for doses that is putting pressure on all supply chains, another significant plus in this instance is Johnson & Johnson is a proven global manufacturer of vaccines – unlike other pharma and biotech companies that are new to this demanding sector, which may partially explain supply problems.

What are the latest indications on supply timelines?
Firstly, it should be noted Johnson & Johnson is an American multinational. Moreover, US president Joe Biden has made its jabs a cornerstone of his plans to speed up vaccination rollout and he has retained a ban on exporting vaccines; a difficulty for European supply as the multinational's supply chain is transatlantic.

On March 10th, he announced his administration had helped broker a deal between Johnson & Johnson and its rival, Merck, to speed up production, that would yield an extra 100 million doses.

At least from an EU perspective, French pharmaceutical giant Sanofi has stepped in to provide a factory near Lyon to make doses, where it says it has the capacity to make up to 12 million doses a month.

All told, it has seven of its own factories in the US and Europe, scheduled to make 1 billion doses this year.

The company told the EU last week that issues had arisen with vaccine ingredients and equipment, which meant it was “under stress” to meet its goal of delivering 55 million doses by the end of June. It told the EU vaccine steering committee, it still intends to deliver 200 million doses of the vaccine to the EU this year, starting in the second quarter.

That means it will not arrive in Ireland until next month. A total of 3.8 million vaccine doses of all approved types are expected to be delivered in the second quarter, including 600,000 Johnson & Johnson doses. A total of 2.19 million Johnson & Johnson jabs in total have been secured under purchasing agreements for this year; enough to vaccinate half the Irish population.

How does the Johnson & Johnson vaccine differ from other vaccines?
It is a "viral vector vaccine", similar to the Oxford-AstraZeneca jab. It uses a modified cold virus, which is proven technology, the adenovirus in this instance has been modified so it cannot replicate.

The vector 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. The approach is very similar to a successful Ebola virus vaccine it has developed.

How effective is it?
This vaccine has a 66 per cent efficacy rate for preventing moderate and severe disease, lower than the first shots approved from Pfizer-BioNTech and Moderna, but above the minimum bar of 50 per cent set by regulatory authorities.

After it was approved in the US earlier this year, it was being dismissed in some quarters as “an inferior product that may not be worth getting”. But it’s effectiveness in countering severe illness was shown to be even more pronounced. In addition, it performs well in all age groups and across a wide range of ethnic backgrounds.

The bottom line is nobody should have any reservations about receiving it. However, given those supply-chain difficulties which have impacted on Johnson & Johnson too – notably at its main manufacturing facilities in the US – it is hard to predict how long we have to wait for it to have an impact here.

That said, once its rollout accelerates in Ireland, it is likely to out-perform its current rivals because of that single-dose advantage in quickly building immunity.

What is the difference between single- and double-dose vaccines?
Vaccines hinge on the memory of your immune system. After vaccination for Covid-19, your immune system continues to store information on the spike protein. If exposed to the novel virus, your immune system uses this stored information to respond and protect you from the virus.

Some vaccines are shown to be more effective when given as double doses. The first dose starts the process of building up protection, the second significantly reinforces this protection.

The entire immunity process usually takes a few weeks to be fully activated after the second dose. During early trials, researchers found the Pfizer-BioNTech and Moderna mRNA vaccines provoked a relatively weak immune response when given as just one dose.

However, there was a stronger immune response when a second dose was added. Vaccines that need more than one dose are not uncommon, while others are demonstrably effective as a single dose.