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On Monday, the third corona vaccine maker announced the first results of larger studies in humans. Based on this, the vaccine, which British pharmaceutical manufacturer AstraZeneca developed in cooperation with the University of Oxford, could protect about 70 percent against Covid-19 disease. Information on efficacy varies greatly depending on the vaccination schedule, that is, the type and dose with which the vaccination is carried out.
In a press release, the developers announced the interim results of two clinical studies. In a combined phase II and phase III trial, 2,741 subjects in the UK received either the vaccine or an ineffective placebo. The vaccination was carried out in two steps. Physicians first administered a half dose of the active ingredient to subjects in the vaccination group and a full dose a month later.
Effectiveness between 60 and 90 percent
According to the press release, 90 percent of Covid 19 cases in the vaccine group could be prevented in this way. However, it is unclear how many Covid 19 illnesses there were in absolute terms among those vaccinated with the active ingredient compared to the placebo group. The data should be published in the next few days. Only then can you tell which database the number is based on.
Before a vaccine is approved, it must be clinically tested in three phases. In order for the Paul Ehrlich Institute to approve a possible vaccine for a clinical study in humans, the manufacturer must first submit data that the substance has already been sufficiently tested preclinically, for example, in animal experiments.
Phase I: The vaccine is given to a small group of healthy volunteers. It is observed if the agent reaches the target area on the body and no acute side effects occur.
Phase II: Only if phase I was successful can the phase II vaccine be administered to a greater number of participants who come from the risk group. In the case of Covid-19, they would be the elderly or people with previous illnesses. This phase tests the effectiveness of the vaccine to prevent the disease and the appropriate dose.
Phase III: The vaccine can then be tested on a representative group of volunteers: up to 10,000 subjects will be vaccinated. In phase III, the efficacy, safety and dosage of the vaccine is confirmed. Adverse events, such as a particularly severe course of the disease due to the administration of the vaccine, can be ruled out.
An efficacy of 90 percent would be in an order of magnitude similar to that claimed by the manufacturers Biontech / Pfizer and Moderna for their vaccines. They name an effectiveness of up to 95 percent (read more about this here and here), Biontech and Pfizer have already applied for emergency approvals in the US.
In a second vaccination schedule, however, the AstraZeneca / Uni-Oxford vaccine performed significantly worse. In a phase III study with 8,898 test subjects in Brazil, experts administered two full doses of the vaccine. The effectiveness here was around 60 percent.
On average, the vaccine has so far shown 70 percent effectiveness in both studies, according to the company. The figures are based on a total of 131 cases of Covid-19, most of which occurred in the placebo group, but also affected those vaccinated with the active ingredient more frequently than in studies by the other manufacturers.
No serious side effects
Biotech / Pfizer and Moderna had released the data from their corona vaccination studies after a similar number of cases. However, they have already vaccinated more people overall, so they have a larger data set on side effects, for example.
However, AstraZeneca is confident: There were no serious side effects among those vaccinated, he said. Previously, the company had twice had to interrupt its vaccination studies because the test subjects became ill, but the experts found no causal link to the vaccine.
The company will also soon request approvals in various countries around the world and will register the vaccine with the WHO for rapid use in the poorest countries. Phase III studies will also be tailored so that the half-dose vaccination schedule is tested in larger studies.
Simple storage advantage
The base of the AstraZeneca / Uni-Oxford vaccine called AZD1222 or ChAdOx1 nCoV-19 is a weakened cold virus of chimpanzees. It contains genetic material for a surface protein with which the pathogen Sars-CoV-2 attaches to human cells. When the immune system comes into contact with this protein, it specifically forms antibodies and T cells.
Unlike the Biontech / Pfizer and Moderna vaccines, the agent does not belong to mRNA vaccines, but to so-called vector vaccines. The principle has been known for a long time and has a decisive advantage: the vaccine can be stored in the refrigerator and, unlike mRNA products, it does not need a negative double-digit temperature (read more here).
This makes it easy to store and transport. This could make the vaccine important, even if it is slightly less effective.
“AZD1222 is robust and easy to use, like the worker bee among potentially available vaccines against Covid-19,” Clemens Wendtner from Munich Clinic Schwabing told the Science Media Center. The vaccine can be safely stored in the refrigerator between two and eight degrees Celsius for six months. “This should facilitate vaccination campaigns in countries with fewer resources for complex cold chains.”
In any case, the world does not get along with a corona vaccine, vaccine researcher Andrew Pollard of the University of Oxford, who participated in the vaccination trial, told a news conference. No company has the capacity to provide enough vaccines for the entire world population in the short term.
AstraZeneca has already prepared to mass produce its vaccine. According to production manager Pam Cheng, 200 million cans could be delivered this year. The production of three billion cans will be possible in 2021. Shifting production into half-can parts on short notice is not a problem.
Unclear details
However, as with the other manufacturers, the AstraZenca study cannot answer all questions. It is not yet clear how reliably vaccines prevent not only Covid-19, but also infections with the Sars-CoV-2 coronavirus.
According to a press release from the University of Oxford, there are initial indications of protection against infections in relation to the active ingredient it helped develop. However, the final results are not yet available.
Also, there is no public data yet that shows how well vaccines work in different age groups. An evaluation of the first results of its vaccination study in Great Britain published last week by Oxford researchers in the trade journal “The Lancet”, however, at least raises hope that the vaccine will also work well in the elderly.
In the phase II study, there was a good immune response in participants younger and older than 56 years, the researchers write. The vaccine was even better tolerated by the elderly than the very young. According to the information, about 240 of the 560 healthy study participants included in the analysis were over 70 years old.
According to AstraZeneca and the University of Oxford, there were no severe courses of Covid-19 in their studies among those vaccinated with the active ingredient. How rare they were compared to the placebo group remains open. Therefore, it is not possible to say how many serious illnesses were prevented by the vaccine.
The full data from the studies, which is not yet public, should soon provide answers to some of these questions.
Mystery of the half-dose benefit
However, researchers still do not know why, of all things, the vaccination schedule with half doses at the beginning has shown better effectiveness. That wasn’t immediately obvious, Gerd Fätkenheuer from the Cologne University Hospital explained to the Science Media Center. “Is that a purely coincidental effect? Or are there immunological factors that justify it? “
Clemens Wendtner from the Schwabing Clinic in Munich suspects that the immune system may react to the monkey-carrying virus and that the effect of the vaccine is weakened as a result. If the first dose of the vaccine is too high, the body can fight the carrier virus with the second vaccine.
The Oxford Pollard vaccination researcher explained that vaccines for infants, whose immune system does not initially know of any pathogens, are often more effective with a lower starting dose. It is conceivable that it is similar in adults who come in contact with an entirely new virus.
However, experts agree that more data is needed for a clear answer.
