As COVID-19 cases caused by the novel coronavirus, SARS-CoV-2, continue to surge, U.S. drugmaker Pfizer announced early results indicating that its vaccine is more than 90 percent effective. The announcement represents a major milestone toward controlling the COVID-19 pandemic. However, these are interim results and continued patience and vigilance are required to see a safe and efficacious vaccine to the finish line. There are currently ten other COVID-19 vaccines in late-stage trials.
Three coronaviruses have emerged in the human population in the last two decades: severe acute respiratory syndrome (SARS) in 2003, Middle Eastern respiratory syndrome (MERS) in 2012, and now SARS-CoV-2, which causes COVID-19. The success of SARS-CoV-2, relative to its cousins, SARS and MERS, is due to the fact that it is highly infectious among humans and can be transmitted for days prior to the onset of symptoms.
SARS-CoV-2 emerged into the human population in late December 2019 in Hubei, China, initially described as pneumonia of unknown etiology. The first cases appeared in the U.S. in January 2020, and it has since become a global pandemic. To date, COVID-19 has sickened over 50 million people worldwide, killing over 1.2 million. The U.S. alone now has over 10 million cases, increasing by over 100,000 per day, and has suffered more than 238,000 deaths. At its current pace, COVID-19 is on track to overwhelm the U.S. health care system before 2021. A vaccine is our best chance for herd immunity sufficient to end the pandemic.
Vaccines against viruses, such as influenza and measles, use attenuated or killed viruses or pieces of those viruses to induce an immune response resembling that of an actual infection. However, the Pfizer vaccine, similar to the Moderna technology, is novel because the genetic material of the virus is injected into the muscle. Cells in the muscle will then produce the protein comprising the surface of the SARS-CoV-2 virus particle. These proteins are recognized by the immune system as foreign and an immune response is mounted against it as if there was an infection. In the event of a subsequent actual infection, the immune response is primed to act — ready to target and eliminate the invading virus. Vaccines prevent infection but cannot cure an ongoing infection.
Pfizer plans to seek approval from the Food and Drug Administration for emergency authorization for its 2-dose vaccine. The vaccine is currently being tested in 44,000 people. No serious adverse effects or safety concerns have been observed. Pfizer is on track to manufacture enough vaccine to immunize 15-20 million people by 2021. However, the distribution of those doses globally still represents a significant challenge. And, as the vaccine is based on RNA, the genetic material of SARS-CoV-2, it is fragile and must be maintained at ultralow temperatures.
The Trump administration launched Operation Warp Speed to develop a vaccine by the end of 2020. However, many vaccine makers including Pfizer, refused federal support, seeking to distance themselves from a political agenda that raised concerns of dangerous shortcuts in vaccine development.
The ability to develop this novel vaccine is founded on 70 plus years of careful research by thousands of scientists who made the basic discoveries that were needed to understand cell biology, immunology and virology. The speed at which the vaccine was developed, within a year of emergence of the virus, is a triumph for fact-based, data-driven science. The Pfizer vaccine is the result of a collaboration between Pfizer and the German drugmaker BioNTech.
With this announcement, we can see a glimmer of light toward ending the COVID-19 pandemic. While these early results are cause for optimism, long-term safety and efficacy data have not been collected. Further, it is too early in the trial to know how long immunity induced by the vaccine will last. Will it be long term or will we need frequent boosters?
Further, vaccinating the U.S. population, much less the world population, will require years. The first doses of vaccine will go to first responders and health care workers. Additionally, the ability of the vaccine to approach communal immunity will require that more than 50 percent of the population be vaccinated. Given the high level of vaccine reticence in the U.S., this number may be difficult to achieve. A major goal of the Biden COVID-19 Task Force must be to develop trust in a vaccine once it is proven safe and effective. Clear, data-driven messaging will be key to developing trust.
In the interim, we must keep public health at the forefront — using common sense approaches to stop the spread of SARS-CoV-2 by combining the mitigation strategies of distancing, masking and disinfection of hands and surfaces. The vaccine announcement gives us hope, but it will still require years to effectively stop the spread of COVID-19.
Felicia Goodrum Sterling is a virologist, president-elect of the American Society of Virology, and a fellow of the American Academy of Microbiology. She is a professor and scientist at the University of Arizona. James Alwine is a virologist and a fellow of the American Academy for Microbiology and of the American Association for the Advancement of Science. He is a professor emeritus at the University of Pennsylvania and a visiting professor at the University of Arizona.