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Pfizer’s COVID-19 vaccine is 90% effective, according to preliminary trial data

The race to make a COVID-19 vaccine in the United States has entered its final sprint, with one of the leading candidates being the first to publish preliminary results showing that its vaccine is more than 90 percent effective in preventing people from getting sick. coronavirus.

The long-awaited announcement came in a November 9 press release detailing the results of an interim analysis of an ongoing Phase III clinical trial comparing the vaccine developed by global pharmaceutical company Pfizer and German biotechnology company BioNTech with a placebo.

COVID-19 cases are skyrocketing worldwide and some countries are turning to blockades and other drastic measures to curb the spread of the virus. As of Nov. 9, more than 50 million people have become infected worldwide – including more than 10 million in the United States – and more than 1.2 million people have died from the disease.

“We are one step closer to bringing people around the world a much-needed breakthrough to help end this global health crisis,” said Pfizer President and CEO Albert Bourla.

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Preliminary data have not yet been reviewed by other scientists and details have not yet been published. But among people who received the vaccine, there were more than 90 percent fewer symptomatic cases of COVID-19 than among people who received a placebo, the companies reported. It is not yet clear how the vaccine may work between different age groups, including children and the elderly, and whether the vaccine has affected the severity of the disease.

The trial has so far registered more than 43,000 people. Of those participants, 38,955 completed the vaccine regimen, which consists of two injections spaced three weeks apart. At the time of the analysis, which analyzed data seven days after participants received a second dose, a total of 94 people at trial had confirmed coronavirus cases.

The published data did not include how many cases were recorded in each group nor what portion of the nearly 39,000 people who received both doses of vaccine were included in the analysis. The companies had previously said they would conduct a preliminary analysis when 62 people had COVID-19. The reported efficacy rate suggests that most of those who became ill so far were in the placebo group. The researchers plan to conduct a final analysis when a total of 164 cases have been recorded and will follow participants for two years.

The US Food and Drug Administration recommends that COVID-19 vaccines be at least 50 percent effective, meaning that a vaccine should halve COVID-19 cases compared to a placebo (SN: 10/4 / 20). Preliminary analysis suggests that the Pfizer and BioNTech vaccine could surpass that benchmark, but the clinical trial is ongoing so final efficacy could change.

“It’s early, but we can be cautiously optimistic,” says Mark Slifka, a viral immunologist at Oregon Health & Science University in Portland. "By reaching more than 90 percent, that's where we want to see successful vaccines."

To apply for an emergency use authorization, the FDA requires that half of the participants have at least two months of data on the safety of a COVID-19 vaccine after receiving the final dose. For the Pfizer and BioNTech vaccine, that point is expected to reach the third week of November.

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Vaccines from other companies, including one from Moderna, Inc., are expected. based in Cambridge, Massachusetts, are very close (SN: 18/05/20). And countries like China and Russia have approved other vaccines for limited use in their countries, although none have published data from phase III trials to demonstrate how effective they can be (SN: 8/11/20).

Slifka points out that it is unknown whether the effectiveness of the Pfizer-BioNTech vaccine will be maintained over time. ”That 90 percent effectiveness is“ only until day seven (after the last of the two injections). We just need to see if it stays above, at or near that level and if so for how long. And even if it does fall, that doesn’t necessarily mean the vaccine is a failure. He only tells us when we would have to do another reinforcement. "

The Pfizer and BioNTech vaccine contains a viral mRNA, a genetic molecule that cell machinery reads to build proteins. In this case, that mRNA contains the genetic instructions for making the coronavirus ear protein, which helps the virus bind and enter host cells. The nanoparticles encapsulate the mRNA and deliver it to the host cells. These cells then build replicas of the ear protein so that the immune system can recognize it and accumulate a memory of the virus. If a vaccinated person encounters the real virus, their body is ready to send antibodies and other immune cells to fight the virus. The vaccine does not contain any infectious virus that can infect the cells.

Previous clinical trials have shown that the mRNA vaccine produced immune responses in people who could protect themselves against the virus. He and other vaccines also passed the first safety tests indicating that the vaccine did not cause serious side effects (SN: 21/07/20). The vaccine causes some mild to moderate symptoms, such as pain at the injection site, fever, and chills.

“Without a doubt, these are very promising results,” says Brianne Barker, an immunologist at Drew University in Madison, New Jersey. But the statement suggests that the vaccine protects participants from getting sick with COVID-19, that is, having symptoms of the disease loss of smell, fever, or trouble breathing (SN: 02/07/20), but not from coronavirus infection. . This could have implications for whether the vaccine can eventually remove the virus from circulation among people. “It’s possible that a vaccine can prevent disease but still allow it to become infected,” Barker says.

The press release also does not mention whether there was a difference in what the sick people in each group faced. “This could be really important in terms of how this vaccine works in the population,” Barker says.

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