AstraZeneca’s two-dose COVID-19 vaccine exceeded expectations, and it was very effective against symptomatic and serious diseases in a new late-stage trial conducted in part in the USA. The company said it was now seeking permission for emergency use from the Food and Drug Administration. However, the vaccine can still be questioned.
The phase III trial conducted in the US, Peru and Chile found that the vaccine was 79 percent effective in preventing symptomatic diseases, the company reported early Monday. Previous test results suggest that the efficiency can be up to 62 percent.
In the new trial of 32,449 people, two-thirds of the participants were given the vaccine, while the remaining third received a placebo. There were five cases of serious diseases in the trial, all in the placebo group. None of the vaccinated participants required hospitalization.
The company also found no increased risk for blood clotting events or cases of a rare, life-threatening blood clotting event, called CVST, among those vaccinated.
Blood clots
A small number of serious blood clotting events in people who have recently been vaccinated have caused great concern in Europe and other countries, where the vaccine has already been allowed to be used. In the past week or so, more than a dozen countries – including Germany, France, Italy and Spain – have temporarily halted their implementation of AstraZeneca’s vaccine, developed in collaboration with the University of Oxford.
Among the more than 20 million people who have already received the vaccine in the European Union and the United Kingdom, at least 18 cases of CVST (cerebral venous sinus thrombosis) have been reported, in which a blood clot prevents blood from draining from the brain. , which leads to a stroke. There have also been at least seven other cases of people developing blood clots in multiple blood vessels, a condition called disseminated intravascular coagulation, or DIC. Nine of the cases of CVST and DIC resulted in death.
Last week, the World Health Organization and the European Medicines Agency independently reviewed all the data in detail and eventually called on countries to resume use of the vaccine quickly. Both agencies concluded that the risks of serious illness and death due to COVID-19 outweigh the extremely rare risk of blood clotting events.
The WHO and the EMA noted that among the millions of vaccinations, the incidence of blood clotting events – which are common – was lower than would be expected in the general population. They also could not determine if the vaccine caused the cases of CVST or DIC. But they also could not rule out the possibility, especially since most cases in people were younger than 55.
In the EMA’s review, the organizations note:
Based on the pre-COVID figures, it was calculated that less than 1 case of DIC would be expected among people under 50 within 14 days of receiving the vaccine by 16 March, while 5 cases were reported. Similarly, an average of 1.35 cases of CVST could be expected among this age group, while on the same cut-off date there were 12. A similar imbalance was not visible in the older population.
Talmvrae
The new trial results found no cases of CVST, but—as there really is a link – it’s not surprising, based on the extremely low frequency of these events. The trial data contained safety data for about 21,500 vaccines, while the small number of cases outside the trial occurred below 20 million vaccines.
Although the real possibility exists that the cases are merely a statistical attack, some researchers believe that the vaccine – rarely – can cause an autoimmune reaction that explains the diseases, and they have suggested possible treatments. Other researchers also noted that a link between the vaccine and blood clotting events is not unlikely; COVID-19 itself has been linked to blood clotting disorders, and research suggests that the SARS-CoV-2 ear protein may activate immune responses that may lead to clotting.
But much more data will be needed to capture the compound (if there is one), and to find out how such a reaction is caused by the vaccine and who may be affected. Like the other authorized COVID-19 vaccines, the AstraZeneca vaccine only delivers the genetic code for the SARS-CoV-2 ear protein to cells, which can train immune responses to target the virus. The vaccine does this using a non-replicating adenovirus as packaging, similar to the Johnson & Johnson vaccine, which was the latest vaccine approved by the FDA.
For now, the FDA will focus on examining the data and deciding whether to grant an EUA. The agency is likely to look favorably on the efficacy and safety data of the new trial and consider the vaccine as another useful tool in the fight against SARS-CoV-2. However, obtaining public support could be a major obstacle to the vaccine moving forward. Apart from the concerns about blood clotting, the vaccine has stumbled after stumbling block in its clumsy development – from many published trial breaks due to unexplained diseases and mysterious dosage errors in some participants, to recent data suggesting that it may be useless at moderate to moderate COVID-19 caused by the B.1.351 variant.