Those vaccinated with Johnson & Johnson’s single-dose vaccine may need a booster to be protected from the Delta and Lambda variant. This is the suggestion that comes from a study published not in a scientific journal but on the online platform Biorivx, still in pre-print (it means that it has not yet been subjected to peer review), according to which the protection of the single dose could not enough against a variant – the Delta – which is particularly contagious and which in a few weeks – from the beginning of July to today – in the United States has increased from 50 to 83% of estimated prevalence. And that is increasing the cases of contagion in all the countries of Europe, including Italy. To date, however, the American FDA does not recommend the second dose.
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Before moving on to the results, it should be noted that the study was conducted in the laboratory on blood samples and therefore may not replicate the vaccine‘s performance in the real world, and this is also clear to the authors who however conclude that about 13 million people in the US – those injected with Johnson & Johnson, may need a second dose, possibly with an mRNA vaccine, then Pfizer or Moderna. Authors who have no research or economic connection with the pharmaceutical companies that produce vaccines of any kind, as they themselves point out in the study. The opposite conclusion – however – to that of small studies published by Johnson & Johnson just this month, according to which the single dose protects against the variant even at 8 months from inoculation.
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The study compares the amount of neutralizing antibodies produced by mRNA vaccines (for which there is evidence of protection with the double dose against the Delta variant) and those with an adenoviral vector. In light of the emergence of increasingly infectious variants, the researchers investigated the possible loss of efficacy of vaccines. Los tudio analyzed blood samples from 17 people immunized with two doses of the mRNA vaccine and 10 immunized with one dose of J&J. The latter – according to the publication – showed less efficacy than mRNA vaccines and a greater decline in efficacy against Lamba and Delta variants.
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According to the study, a single dose of AstraZeneca – a vaccine similar in type to Johnson & Johnson – shows about 33% efficacy against symptomatic Delta variant disease. Of course, the message – underlines Nathaniel Landau, virologist at NYU’s Grossman School of Medicine – “is not not to vaccinate with J&J. But we hope that a second dose of J&J can be considered either with Pfizer or Moderna”.
According to many experts, the results of the study are not surprising because all vaccines appear to be more effective with two doses. “I have always thought – says John Moore, virologist at Weill Cornell Medicine in New York – that J&J is a two-dose vaccine. And the lower efficacy is now a concern”. And he cites studies in humans and monkeys that point to greater efficacy of the Jannsen product with two doses, rather than the intended single. In addition, the researchers are completely independent from pharmaceuticals, so the study is particularly credible. After all, there are very few single-dose vaccines, “because the second dose is necessary to amplify the level of antibodies – explains Akiko Iwasaki, immunologist at Yale University. And who has been inoculated with the J&J vaccine – explains Dr. Iwasaki – has difficulty to maintain the primary response to immunization in the presence of these variants. A second dose should raise the level of antibodies and counteract the variants. “
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As for a possible future second dose, the choice could fall on the mRNA vaccine, since now some studies have shown a greater efficacy of the so-called heterologous vaccination, with a second dose of mRNA after one with an adenoviral vector vaccine, such as AstraZeneca or J&J .
The data from the new study – however – once again consider only one aspect of immunity, points out Seema Kumar, spokesperson J&J, and in fact the studies sponsored by the pharmaceutical company indicate that the single-dose vaccine “generates a strong and persistent response. even against the Delta variant “.
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