This is really exciting news in the fight against COVID-19.  The Janssen vaccine is effective with a single dose, in contrast to other approved vaccines which require 2 doses.  In the clinical trials (conducted in the US, South Africa and Brazil), this vaccine demonstrated protection against several of the emerging variants of concern which is also very encouraging.  This provides another vaccine in the global fight against this pandemic.

The authorisation of another vaccine for use in the EU is very welcome – the greatest barrier to rolling out the vaccines, so far, has been the availability of vaccines.  This new addition can only add to the quantity of vaccine available in the EU, as well as providing another alternative if there are hitches with the supply or use of other products.

As I understand it, the new vaccine is a Johnson and Johnson product, manufactured by its Janssen subsidiary.  This is why you sometimes see it referred to as the Johnson and Johnson vaccine, and sometimes as the Janssen vaccine – which can be confusing.  I shall refer to it as the J&J/Janssen vaccine.

This decision was to be expected following the vaccine’s licensure in the USA – the Vaccines and Related Biological Products Advisory Committee report provides copious information about it.  Like the Oxford/AstraZeneca and Sputnik-V vaccines it is a viral vector, using a replication-deficient adenovirus (they all use different adenoviruses) to deliver viral DNA which is translated, after injection, cells’ cytoplasm into the SARS-CoV-2 spike protein: the end product (if you like) in all of the currently available vaccines is the same spike protein.

There has been hesitation in some quarters because the headline efficacy for the vaccine has not been reported as quite as high as other vaccines.  This hesitation is misplaced: the vaccines have not been tested “head-to-head”.  They have used different trial protocols, at different times (with different virus variants circulating), and in different populations.  One of the populations in which The J&J/Janssen product was tested was in South Africa, in a population with a higher prevalence of HIV infection for example.  As far as we can tell, there is little if any difference in the efficacy of this product compared to the other vaccines already available in the EU and UK.

The big difference between the marketing authorisations of this vaccine compared with other vaccines on the market is that this is intended as a single-dose vaccine.  It will be very interesting to see how this plays out over time.  We know that the response to a single dose of all of the available vaccines has been better than was originally expected.  It is possible that other vaccines might have been recommended as single-dose vaccines if the trial period had been extended further.  It is also possible, as time goes by, that we will see immunity to the J&J/Janssen product wane over time.  If this happens it will be detected on the post-implementation surveillance programmes that are in place in many countries, not least in England2.  It is possible – as happened e.g. with human papillomavirus (HPV) vaccine that immunisation schedules will evolve as we acquire more knowledge about the immunity induced by the vaccines (and also as new vaccines are introduced to cover new variants of the virus).

It is also possible that, as we learn more, the optimum schedule will vary for particular groups of patients – patients with cancer or on immunosuppressive treatment for other conditions, for example, might possibly be better served by a different vaccination regime.

For now, we can be very happy that this single-dose vaccine is now available in the EU.

1 Vaccines and Related Biological Products Advisory Committee. FDA Briefing Document. Janssen Ad26.COV2.S Vaccine for the Prevention of COVID-19: Federal Drug Administration, 2021 (26 Feb); 1-62 (https://www.fda.gov/media/146217/download or via https://www.fda.gov/advisory-committees/advisory-committee-calendar/vaccines-and-related-biological-products-advisory-committee-february-26-2021-meeting-announcement).

2 Public Health England. COVID-19 vaccine surveillance strategy: Public Health England, 2021 (11 Jan); 1-22 (https://www.gov.uk/government/publications/covid-19-vaccine-surveillance-strategy).

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