The expansion of the delta variant is making clear the importance of the second dose of all vaccines. A study that has just been published in the ‘New England Journal of Medicine’ (NEJM) indicates that the effectiveness of Pfizer with one dose is 35.6% and with two it reaches 88%. In the case of AstraZeneca, it goes from 30% to 67%. In general, vaccines protect almost the same against this new version of the virus that is prevailing in much of the world as against the traditional strain, because the decrease is very slight and they continue to be excellent for avoiding serious illness. However, the authors of this work emphasize the importance of completing the pattern. Even the health authorities are already preparing for the possible administration of a third dose from Pfizer and Moderna.
Against this background, one wonders what happens to Janssen (Johnson & Johnson), the single dose vaccine. In this case, the guideline is complete with a single prick and has thus been approved by different regulatory entities, including the European Medicines Agency (EMA). However, how different is this drug from its competitors? Are we as protected with a single dose of this vaccine as with two of the rest? The debate is served.
EFE
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“In the end they will have to take two doses,” says Marcos López Hoyos, president of the Spanish Society of Immunology (SEI), in statements to Teknautas. In fact, the single dose regimen for this vaccine that uses a human adenovirus “It caught our attention from the beginning”he acknowledges, “but the clinical trials went very well and there was no evidence to refute them.” However, seeing that all the other vaccines require two pricks compared to the delta variant “it makes perfect sense to think that with Janssen the same will happen “, because” you need more protection “.
The truth is that this drug was already presented in its day with some disadvantage in its efficacy data. While clinical trials of Pfizer and Moderna gave a spectacular 95%, in the case of Janssen, who carried out a large study with 44,000 participants, was reduced to 66%. However, when analyzing the data in detail, it was possible to verify that this figure was much better than it seemed, since the protection was 85% against severe cases and 100% against death. In addition, the appearance of the first worrisome variants reinforced this vaccine, because it maintained very good data against the mutations of the virus that arose in South Africa or Brazil.
In short, the results were good enough for the EMA to give it the green light on March 11 with a single dose. In fact, early studies indicated that antibody levels grew over weeks. until reaching the maximum at 57 days, that is, almost two months later. In this way, the researchers considered that one dose could be sufficient and this was confirmed by the regulators. In the case of AstraZeneca, another adenovirus vaccine, the data with one dose were much lower, so in that case there was no question that it was better to give two. “Although they have the same foundation, the preparation can give rise to these differences,” says the president of the SEI.
However, it is a decision that is made at a given moment and that not only responds to scientific criteria, but also strategic from a commercial point of view. That is, it is not necessarily derived from the characteristics of the product, but rather it is a bet of the pharmaceutical to position itself in a market where they were no longer going to be the first: obviously, a single dose is an advantage over the competition, as is another of its characteristics: it can be distributed under normal refrigeration conditions, without the need for deep freezing , such as messenger RNA (Pfizer and Moderna).
“I think they did it as a strategy, we always thought that the single dose was a commercial issue,” says López Hoyos. In fact, Janssen has launched a second double dose clinical trial whose data are expected, in principle, for this same summer. The problem is that given the advances in vaccination “it has been difficult for them to recruit the participants.” In any case, “they thought that the benefit of a second dose was not going to be much greater,” says Jaime Pérez Martín, an expert from the Spanish Association of Vaccination (AEV), so the decision “was a mixture, on the one hand there were the scientific data that said that the protection was sufficient and, on the other hand, their strategic commitment.
More data is missing
The emergence of the delta variant raised doubts about immunization against covid, but in the case of the most widely distributed vaccines, such as Pfizer and AstraZeneca, it is easier to find an abundance of data in real population that support its effectiveness, at least , if the pattern is completed. In the case of Janssen, the data is less consistent and even contradictory. At the beginning of July, Johnson & Johnson he put out his chest by ensuring that the neutralizing antibody response against the delta variant was even better than against the South African variant. In addition, they cited another study that indicated that the level of protection with their vaccine is maintained and even improves eight months later. In contrast, a New York University study finds that protection against the delta variant leaves a lot to be desired compared to the double dose of other vaccines, so the authors bet on boosting it with an additional dose.
The problem with all these studies is that they are preliminary publications, not peer reviewed, and that offer laboratory data: experiments with blood of vaccinated people that is exposed to the virus, interesting from a scientific point of view but not definitive to draw conclusions about the true effectiveness of the vaccine. “We must have more evidence and above all we must have data from real life”, that is, “from epidemiological data”, highlights the immunologist from the SEI.
“The data we have is few,” agrees Pérez Martín, but in his opinion the serological evidence (antibodies) does suggest that Janssen would continue to be effective against the delta variant even with the current single dose regimen. In spite of everything “regardless of the variable there are those who consider that it is very probable” that a second puncture will end up being recommended. “The desirable thing is that it was not necessary,” he adds.
Scientists taking second from Pfizer
However, faced with this dilemma, positions such as that of the prestigious Canadian virologist Angela Rasmussen, a researcher at the University of Saskatchewan, draw attention. After injecting Janssen in April, she recently had a second dose of Pfizer. As explained, it is not known to what extent the Johnson & Johnson vaccine is effective against delta variant and, in addition, a heterologous regimen (mix vaccines) “It is safe and produces strong immune responses.”
In his opinion, vaccinating completely is important to stop the new variants and it is not necessary to wait for more evidence. “Sometimes public health requires making tough decisions without a comprehensive data set to back it up,” defend on Twitter, but gives the example of combination of AstraZeneca and Pfizer to consider that this case is very similar, so he recommends that other people follow his example.
On USA The debate has been open for weeks, particularly since Andy Slavitt, former medical adviser to President Joe Biden, launched the idea of tightening the protection of those vaccinated with Janssen. For Michael Lin, a researcher at Stanford University, “there is no doubt” that these people “they are less protected”. The case of Jason Gallagher, an infectious disease expert at Temple University in Philadelphia, is especially significant, because he was one of the volunteers who participated in the Johnson & Johnson clinical trial, so he received his one-time dose in the month of November. Months later, seeing the data of infections that the delta variant was causing in the United Kingdom, he decided to give himself a new injection, but this time from Pfizer.
What are the options
In any case, the experts consider that it is convenient to reassure the population, since all vaccines protectespecially in the face of serious illness. Of the four authorized by the EMA, the least used in Spain It is precisely that of Janssen, of which almost 1,700,000 doses have been administered. Would it be worth giving them a booster dose just to optimize already good protection? Probably, the evolution of the pandemic will be decisive in the decision. “It will probably be better to vaccinate twice,” says López Hoyos, but it cannot be ruled out that things remain as they are. In fact, at the moment, no agency has chosen to recommend that solution, not even the Centers for Disease Control and Prevention (CDC, for its acronym in English) in the US, where it has been raised more strongly.
If that scenario becomes a reality, the debate would reopen as to whether the second dose would have to be of the same drug or with a messenger RNA vaccine, as happened with AstraZeneca. Having data from scientific studies would help a lot to make the decision, but at the moment experts only hope that the clinical trial with two doses of Janssen will be published. A study of similar dimensions evaluating the heterologous regimen, that is, a second dose of Pfizer after the first of this vaccine.
López Hoyos recalls that in this approach it is also necessary to take into account the “hybrid immunity”, increasingly important given the high contagion figures that are being reached in the fifth wave. This concept refers to people who become infected and who subsequently receive a dose of the vaccine. In that case, that single prick would suffice, not just for Janssen but for the other drugs as well. In fact, it is proven that the infection linked to the vaccine “induces a greater response”, he recalls.
In short, the discussion about the need for booster doses is still open, but with very different perspectives depending on each vaccine. Although some experts consider the need for a third dose of Pfizer or Moderna (except for the most vulnerable, immunosuppressed or very old), the Government is preparing for it, according to confirmed last friday Minister Carolina Darias, and even for the possible vaccination every year. Instead, the debate over reinforcing Janssen is out of focus but seems even more urgent.
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