The Atlanta Journal-Constitution
Why COVID-19 vaccine looks near
Only one of many needs to prove safe, effective to be made available.
spike protein prevent infection
A vaccine will protect, in part, by inducing the production of antibodies against the spike protein on the surface of SARS-CoV-2, the virus that causes COVID-19.
The virus needs the spike protein to attach to and enter human cells to reproduce. Researchers have shown that antibodies, like those made by the human immune system, bind to the spike protein, neutralize it and prevent the coronavirus from infecting cells in laboratory culture.
Vaccines in clinical trials have been shown to raise antispike antibodies that block virus infection in cells in the lab.
At least seven companies have developed monoclonal antibodies, laboratory-manufactured antibodies that recognize the spike protein. These antibodies are entering clinical trials to test their ability to prevent infection in those who are exposed, for example, through a household contact.
Monoclonal antibodies may also be effective for treatment. During an infection, a dose of these monoclonal antibodies could neutralize virus, giving the immune system a chance to catch up and manufacture its own antibodies to combat the pathogen.
■ 3. Spike glycoprotein contains multiple targets
The spike protein has many locations where antibodies can bind to and neutralize the virus. That’s good news because with so many vulnerable spots, it will be difficult for the virus to mutate to avoid a vaccine.
Multiple parts of the spike would need to mutate to evade neutralizing anti-spike antibodies. Too many mutations to the spike protein would change its structure and render it incapable of binding to ACE2, which is key to infecting human cells.
■ 4. We know how to make a safe vaccine
Safety of a new COVID-19 vaccine is improved by researchers’ understanding of potential vaccine side effects and how to avoid them.
One side effect seen in the past was antibody-dependent enhancement of infection. This occurs when antibodies don’t neutralize the virus but instead allow it to enter into cells via a receptor intended for antibodies. Researchers have found that by immunizing with the spike protein, high levels of neutralizing antibodies can be produced. This lessens the risk of enhancement.
A second potential problem posed by some vaccines is an allergic reaction that causes inflammation in the lung, as was seen in individuals who received a respiratory syncytial virus vaccine in the 1960s. This is dangerous because inflammation in the lung air spaces can make it difficult to breathe. However, researchers have now learned how to design vaccines to avoid this allergic response.
■ 5. Several different vaccines in development
The U.S. government is supporting the development of several different vaccines via Operation Warp Speed.
The goal of Operation Warp Speed is to deliver 300 million doses of a safe and effective vaccine by January.
The U.S. government is making a major investment, committing $8 billion to seven different COVID-19 vaccines.
By supporting multiple COVID-19 vaccines, the government is hedging its bets. Only one of these vaccines needs to prove safe and effective in clinical trials for a COVID-19 vaccine to be made available to Americans in 2021.
■ 6. Vaccines passing through phase I and II trials
Phase I and phase II trials test if a vaccine is safe and induces an immune response. Already the results to date from three different vaccine trials are promising, triggering the production of anti-spike neutralizing antibodies levels that are two- to fourfold higher than those seen in people who have recovered from COVID-19.
Moderna, Oxford and Chinese company CanSino have all demonstrated the safety of their vaccines in phase I and phase II trials.
■ 7. Phase III clinical trials are underway
During a phase III trial, the final step in vaccine development process, the vaccine is tested on tens of thousands of individuals to determine if it works to prevent infection with SARS-CoV-2 and that it is safe.
The vaccine produced by Moderna and the National Institutes of Health and the vaccine from Oxford-AstraZeneca began phase III trials in July. Other COVID-19 vaccines will be starting phase III within weeks.
■ 8. Accelerating vaccine production and deployment
Operation Warp Speed is paying for the production of millions of doses of vaccines and supporting vaccine manufacturing at an industrial scale even before researchers have demonstrated vaccine efficacy and safety.
The advantage of this strategy is that once a vaccine is proved safe in phase III trials, a stockpile of it will already exist, and it can be distributed immediately without compromising full assessment of safety and efficacy.
This is a more prudent approach than that of Russia, which is vaccinating the public with a vaccine before it has been shown to be safe and effective in phase III.
■ 9. Vaccine distributors are being contracted now
McKesson Corp., the largest vaccine distributor in the U.S., has already been contracted by the Centers for Disease Control and Prevention to distribute a COVID-19 vaccine to sites — including clinics and hospitals — where the vaccine will be administered.
I believe that it is realistic that we will know sometime in late 2020 whether some COVID-19 vaccines are safe, exactly how effective they are and which ones should be used to vaccinate the U.S. population in 2021.