10.25 p.m., July 31, 2020
The question of whether SARS-CoV-2 vaccines protect people against infection with the Covid-19 pathogen is currently being investigated in two large efficacy studies with placebo control. The results are still pending. The US biotech company Moderna and the pharmaceutical company Janssen-Cilag (Johnson & Johnson) have now been able to demonstrate a protective effect of their candidate vaccine in monkeys.
A first study of a protective effect of Moderna’s potential vaccines was published in the New England Journal of Medicine. The company is driving the development of an mRNA vaccine against Covid-19 together with the US National Institute for Allergies and Infectious Diseases (NIAID; Head: Anthony Fauci). The efficacy study with 30,000 subjects was only started a few days ago.
Even before such studies, animal models can be used to collect clues as to whether a potential vaccine works or not. This is done by immunization with a candidate vaccine and subsequent experimental exposure of the animals to the pathogens. It is then checked whether the attempted infection “addresses”. In the United States, the question of whether SARS-CoV-2 vaccines could not be organized in humans as subjects with an artificially induced attempted infection was even discussed in the past few weeks. That would be ethically very problematic because there is no successful causal treatment against Covid-19.
NIAID scientists basically did just that with the Moderna vaccine on 24 Rhesus macaques. Eight were given ten micrograms of the vaccine at intervals of four weeks, eight each at one hundred micrograms, the third third only twice as saline as placebo. “Four weeks after the second vaccination, the upper and lower airways were exposed to a high dose of SARS-CoV-2,” the New England Journal of Medicine said.
For two days, the Covid 19 pathogens were discovered in only one of the animals immunized with the different vaccine doses. In the placebo group, this was the case for all eight animals. The concentration of neutralizing and thus protective antibodies against SARS-CoV-2 formed by the really vaccinated animals was twelve to 84 times higher than in the animals which survived the infection without effective vaccination.
The authors wrote: “The ability to reduce virus replication in both the upper and lower respiratory tract has important implications for vaccine-induced prevention and transmission of SARS-CoV-2 disorders.”
The Moderna candidate vaccine is a so-called mRNA vaccine, in which people are injected with the genetic material for virus components. The cells of the immunized are then supposed to produce these virus proteins. These antigens in turn should ultimately lead to an immune response. No vaccine on this basis has yet been approved worldwide.
The pharmaceutical company Janssen-Cilag (pharmaceutical and vaccine company of the US conglomerate Johnson & Johnson) reported very similar results – also on non-human primates – on Friday with reference to a publication in “Nature”.
“Johnson & Johnson announced today that its leading vaccine candidate has protected from infection with SARS-CoV-2, the virus that causes Covid-19, in preclinical studies. Neutralizing antibodies showed that the vector-based vaccine adenovirus serotype 26 (Ad26 ) caused a reliable immune response in non-human primates (NHPs), so that infection was prevented and the lungs were completely protected from the virus, “it said in a broadcast.
This candidate vaccine consists of artificially modified, safe and non-disease-causing adenovirus particles onto which the antigens necessary for an immune reaction against SARS-CoV-2 are grafted. Since the temporary emergence of SARS infections and SARS diseases in 2002, scientists around the world have assumed that a protective immune response against such coronaviruses is most effective after the immune system is confronted with the spike surface protein (S protein) Pathogen or parts thereof arise. This also seems plausible because the immune system in pathogens of all kinds initially only registers their surfaces as foreign.
“Based on the convincing preclinical data, the first phase 1 / 2a clinical trial in humans with the vaccine candidate Ad26.COV2.S was started on healthy volunteers in the USA and Belgium last week,” said Janssen-Cilag. As early as September, the company plans to start a phase III efficacy study.
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