Wednesday, February 24, 2021

with its single dose, can Janssen’s vaccine candidate reshuffle the vaccination campaign cards?


Next. It’s Johnson & Johnson’s turn to knock on the door of the European Medicines Agency. The pharmaceutical group, via its subsidiary Janssen, filed an authorization request for its vaccine candidate on Tuesday, February 17, and the regulator specifies that a possible marketing could be discussed in mid-March. In the event of a green light, the Ad26.COV2.S vaccine would then become the fourth serum against Covid-19 used in Europe. Above all, it would be the first single-dose vaccine. A specificity that makes the candidate’s CV very attractive.

“From a logistical point of view, you can campaign by summoning people only once”, emphasizes to franceinfo Marie-Paule Kieny, president of the Vaccine Covid-19 committee and director of research at Inserm. This one-dose vaccination scheme has a clear advantage in terms of streamlining the circuits and improving access to the vaccine. In France, at the end of February, 1.7 million of the 4.3 million appointments will have been devoted to the second injection of the vaccines from Pfizer and Moderna, according to the Ministry of Health. Hence the interest of a single-dose product, to free up niches and speed up the pace.

It is not the technological aspect that distinguishes the candidate vaccine from Janssen, since it uses the same method as that of AstraZeneca or Sputnik V. Here, the genetic sequence encoding the synthesis of the “Spike” protein of the coronavirus is inserted into the genome of an adenovirus (Ad26) previously stripped of its harmful power. The laboratory has been developing its “AdVac” technology for more than ten years. She is already using it for her Ebola vaccine and for all of her virus vaccine projects. In total, “200,000 subjects have already been put in our various clinical trial programs” with Ad26, explains Telma Lery, medical director of infectious diseases at Janssen France, to franceinfo.

Viral vector vaccines guide the synthesis of the “Spike” protein by our own cells, in order to trigger an immune response. But during vaccination, the protein is produced in isolation, independent of the coronavirus. It can therefore appear in a different configuration from the proteins present on the surface of Sars-Cov-2. The manufacturer corrected this by testing ten “genetic inserts”. Until obtaining the synthesis of a protein with the closest possible configuration to that of the coronavirus.

After the good results obtained thanks to this sequence “optimized”, and “in a pandemic context”, Janssen researchers decide to test the single dose in their large-scale trial, says Telma Lery. At the end of January, the industrialist presented (in English) the partial results of its trial involving more than 40,000 participants. After an injection, the efficacy against moderate to severe forms reached 72% in the United States, 66% in Brazil and 57% in South Africa. Janssen also announces an efficacy of 85% against severe forms of the disease, regardless of the region of the world. Encouraging results when compared to those of competitors: after two doses, the effectiveness of AstraZeneca vaccine reaches between 62% and 70%, according to the studies. “Their vaccine may be more effective than two doses of AstraZeneca vaccine”, explains Claire-Anne Siegrist, director of the vaccinology center of the Geneva university hospitals.

The laboratory therefore seems to have scored a point and has not been asked to praise its success. “Single-dose vaccines are considered by the World Health Organization as the best option in a pandemic situation. They improve vaccine access, distribution and compliance “, said Paul Stoffels, Chief Scientific Officer of Johnson & Johnson. With this product, “a billion doses of vaccine would translate to a billion people vaccinated”, rejoiced on CNN (in English) virologist Dan Barouch, who participated in the development of the vaccine candidate.

“It’s a competitive advantage for them”, summarizes Marie-Paule Kieny, but also “for the payer, for the vaccinated people and for the public institutions in charge of vaccination”. However, some groups have already experienced failures in their quest for the single dose. The Merck laboratory, for which that was the big goal, had to throw in the towel in January for its two vaccine projects. There are still contenders: the mayor of Moscow (Russia) Sergei Sobyanin has just announced the recruitment of new participants for the phase 3 trial (in English) involving a single injection administration of Sputnik V. AstraZeneca’s intentions are not clear on this point.

In parallel, Janssen nonetheless secured his back with an impending phase 3 study on a two-dose regimen. This essay, Claire-Anne Siegrist believes, has rather “to see if [le fabricant pourrait] compete with the 95% efficiency of RNA vaccines or Sputnik V “. According to preliminary data, underlines Inserm, “the vaccination schedule in two doses multiplies by 2 to 3 the amount of antibodies produced against Sars-Cov-2”. Marie-Paule Kieny adds that “if the efficacy after two doses was significantly higher, the vaccination schedule could be adjusted according to age or risk factors”.

The booster dose of other vaccines is not a gadget: it helps to consolidate neutralizing immunity and to register it over time. “In an epidemic context, the question is therefore to know what is the durability of the response and the memory”, underlines in particular the immunologist Brigitte Autran, of the Covid-19 Vaccine Committee, contacted by franceinfo. At this stage, the manufacturer explains that he lacks hindsight to provide precise data on this point, but he does not observe a drop in the quantity of antibodies in the first three months.

Marie-Paule Kieny, for her part, believes that “This is not a problem that seems prohibitive for the Janssen vaccine, especially with the other vaccines, we do not know this duration either”. Asked about BFMTV, Alain Fischer, in charge of vaccine policy in France, wants to be more cautious.

“The question arises for other vaccines, but a little more in this case: if we only give one dose, what will be the duration of protection?”

Alain Fischer, in charge of the vaccination campaign in France

on BFMTV

Contacted by franceinfo, the biologist Claude-Alexandre Gustave has other reservations. He underlines the risk of an absence “protective against infection and transmission, as long as neutralization is absent”. In the case of the vaccines from Pfizer and Moderna, he explains, the amount of antibodies is almost maximum after the first dose, but their ability to neutralize the virus is reached a week after the second dose. Janssen is also observing a time of “maturation” the immune response, “including neutralizing antibodies, remote from immunization”, Marie-Paule Kieny analysis. This point still deserves more detailed data.

At this stage, the European green light still seems well under way. If this is the case, the first doses could be delivered at best in April on French territory, specifies the Ministry of Health, which does not exclude “a small possible shift in May”. This single dose “will allow to be inventive on logistics”, he adds, without giving more details. In total, 8.1 million doses of Janssen’s vaccine are expected by the end of June and on that date, they could therefore represent a fifth of the French vaccine strike force.

When it is necessary to space the two injections, for example between 9 and 12 weeks in the case of the AstraZeneca vaccine, it may be difficult to bring back those first vaccinated. The possible arrival of this candidate vaccine should also reshuffle the cards in developing countries. MRNA vaccines are inaccessible in many regions due to their cost and logistical constraints (adapted freezers and secure circuits) to maintain the cold chain. Like the AstraZeneca vaccine, the Janssen vaccine also has the advantage of being stored for several weeks at 2 to 8 ° C.

This explains the interest of the WHO, which announced last December a memorandum relating to the acquisition of 500 million doses of this candidate vaccine (170 million for AstraZeneca, no mRNA vaccine), in the part of the Covax initiative, which aims to ensure equitable access to vaccines for all countries.



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