Florian Krammer, PhD, right, filled out the paperwork needed to participate in Pfizer’s COVID-19 clinical trial and discussed the trial with Judith A. Aberg, MD, left, the Dr. George Baehr Professor of Clinical Medicine, and Chief of the Division of Infectious Diseases for the Mount Sinai Health System.
“Dear world, we have a vaccine!”
Florian Krammer, PhD, Professor of Vaccinology at the Icahn School of Medicine at Mount Sinai recently tweeted this in response to news of the interim results to Pfizer Inc.’s COVID-19 vaccine clinical trial, which showed high efficacy in the final, phase 3 round of human testing. “This is the best news since January 10,” Dr. Krammer added. On that date, China released the genome of SARS-CoV-2, the virus that causes COVID-19. Dr. Krammer’s laboratory at Mount Sinai immediately moved from developing a universal flu vaccine to creating the first test to detect the presence of antibodies to SARS-CoV-2 and the first to measure the amount of antibodies.
By November 17, Pfizer had updated its phase 3 results to report that its vaccine was 95 percent effective against COVID-19, across age, gender, race, and ethnicity demographics. Only one day earlier, Moderna Inc. confirmed that its COVID-19 vaccine candidate had a very high efficacy rate in its first interim analysis of its phase 3 study, prompting Dr. Krammer to tweet, “Dear world, we have a second vaccine.”
Both the Pfizer and Moderna vaccines are based on new RNA technology. Rather than containing pieces of an actual virus, as traditional vaccines do, these vaccines contain molecular instructions in the form of messenger RNA (mRNA) that tell human cells to make the virus’s spike protein, the immune system’s key target for the virus. If all goes well, the patient’s immune system will react by making antibodies to the spike protein—and these antibodies will also latch on to the spike protein of the real virus and disable the virus.
“This is the beginning of the end of the pandemic,” says Dr. Krammer. But important questions concerning COVID-19 vaccines still remain. This fall, he volunteered to take part in the Pfizer COVID-19 vaccine clinical trial under way at Mount Sinai and other locations in the United States and abroad. Like the other 43,538 trial participants, Dr. Krammer does not know whether he received a placebo or the real vaccine, which is how the placebo-controlled, randomized, observer-blinded vaccine trial is designed.
Mount Sinai Today recently asked Dr. Krammer to explain Pfizer’s phase 3 vaccine results.
Why are you enthusiastic about the Pfizer vaccine?
The results from the phase 3 trial have to be seen in the context of preclinical data, phase 1 and phase 2 trials, where Pfizer showed the vaccine worked in nonhuman primates. Also, in early clinical trials the vaccine induced good neutralizing antibody responses. Now, in addition to that, we get efficacy results—reduction of the incidence of disease in the vaccinated group—that are in the 95 percent range. Ninety-five percent is pretty good. Even a vaccine that affords 50 percent protection against severe disease would be positive news.
What questions do you have concerning the Pfizer vaccine?
Right now, Pfizer is reporting that the vaccine has 95 percent efficacy against symptomatic disease. That will likely protect at-risk individuals from severe disease outcomes. But we still don’t know if the vaccine can protect from asymptomatic infection. If it doesn’t, would it stop vaccinated individuals from spreading the virus to others? It will be difficult to determine if the Pfizer vaccine can achieve this, because it would involve routinely testing trial participants for the presence of virus, and you can’t do that with almost 45,000 people. Also, how long-lasting will the protection be? In other words, will the vaccine’s efficacy decrease over time, requiring people to get revaccinated?
Do Pfizer’s interim results bode well for other COVID-19 vaccines in the pipeline?
This is looking good for many of the other vaccine candidates. The fact that Pfizer’s vaccine is based on inducing neutralizing antibodies that protect from symptomatic infection might mean that many other vaccines are likely to work as well. Moderna’s vaccine is almost identical in terms of the immune response. Others are similar too.
What are Pfizer’s next steps?
Now that Pfizer has filed an Emergency Use Authorization application with the U.S. Food and Drug Administration (FDA) and the FDA has authorized the emergency use of the vaccine, it is likely that the vaccine will only be available for high-risk groups and front-line workers at first. Over time more people will get vaccinated but this will take months. Now, while we wait for the vaccine, we must keep the virus circulation down. Mask up, physically distance, and stick to guidelines and regulations.
Do any of these concerns dampen your enthusiasm for the vaccine?
No. From my point of view there is a light at the end of the tunnel. Right now, we need a vaccine that works, even if it would only protect for a few months or doesn’t completely stop transmission. That’s what we need to get halfway back to normal. We’ve been in this for 10 months. We can do it for a few more. We have to be patient.