What We Know So Far About COVID-19 Vaccines

By: Janet Young, MD

With COVID-19 cases soaring to over 150,000 cases a day in the United States, recent announcements that preliminary results for two different COVID-19 vaccines, one developed jointly by Pfizer and BioNTech and another by Moderna, each showed over 94% efficacy was a welcome piece of good news. Along with the enthusiasm, there were questions regarding when COVID-19 vaccines will become available, whether they will be safe, and how the availability of vaccines will impact daily life. This blog is intended to help you understand how authorization for a COVID-19 vaccine may impact your employees and their families.

1. When will the vaccine become available to my employees and their families?
The earliest a vaccine will become available for limited distribution is sometime in December 2020, but the timeframe is dependent on several factors. Both Pfizer and Moderna are expected to submit applications for Emergency Use Authorization (EUA) to the Food and Drug Administration (FDA) in the next few weeks. In their applications, they must provide detailed information regarding the efficacy of their vaccines and at least two months of safety data for half of the trial participants. The FDA is likely to require several weeks to determine whether to authorize one or both of these vaccines.

Next, the Advisory Committee on Immunization Practices (ACIP) will review available data to determine whether to recommend the vaccine(s) given EUA and provide guidance on who should be vaccinated first given that initial supplies of the vaccine(s) will be limited. Most likely, they will recommend that healthcare personnel be the first in line to receive a vaccine, followed by workers in essential and critical industries as well as individuals with high risk for severe COVID-19 disease based on age and underlying medical conditions.1Young, healthy adults are unlikely to receive a vaccine until spring or summer of 2021.

Initially, Pfizer and Moderna clinical trials were restricted to non-pregnant adults. Pfizer is just beginning to enroll children as young as 12, so it is unlikely that there will be enough data regarding the safety and efficacy of COVID-19 vaccines in children for months.2

2. What happened to all of the vaccines from other manufacturers that were in clinical trials? If other vaccines are authorized, how should employees determine which one is best?
In addition to Pfizer and Moderna, there are currently two other manufacturers conducting large scale COVID-19 vaccine clinical trials in the United States – AstraZeneca and Johnson & Johnson. Provided that the results show sufficient efficacy without safety concerns, AstraZeneca and Johnson & Johnson are likely to file for EUAs later this year or early next year.

Initial supplies of any of the vaccines that receive authorization will be limited until manufacturing and distribution are ramped up to meet demand. If more than one vaccine becomes readily available, individuals will need to select the best vaccine in consultation with a healthcare provider based on various considerations, including:

• How well does each vaccine prevent severe disease?
• Are there differences in efficacy of the vaccines based on characteristics like age or comorbid conditions?
• Are there differences in side effects of the different vaccines?
• Are there reasons why a vaccine that requires one dose, rather than two, would be preferable – including access issues and fear of needles? (Note: Among the four vaccines being tested in the United States, the only vaccine requiring a single dose is the Johnson & Johnson vaccine.)

We don’t know yet whether these vaccines will provide temporary protection like the flu shot, or lifelong immunity like the measles vaccine. Once this information becomes available, any differences in the length of immunity conferred by each vaccine will be another consideration.

3. These vaccines were developed so rapidly. How can we be sure the vaccines will be safe?
To receive emergency use authorization from the FDA, COVID-19 vaccine manufacturers are required to have two months of safety data following the last inoculation for at least half of the trial participants. While two months may seem arbitrary or insufficient, researchers at the FDA made this determination by reviewing the timeframe in which adverse reactions occur for other types of approved vaccines. They found that almost all adverse events occurred within six weeks after inoculation.

Manufacturers are ultimately expected to submit safety data for a longer time period following inoculation – at least six months for a sufficient number of participants - to receive traditional FDA approval rather than EUA. The additional data will provide information on any unexpected, later adverse events. Additionally, vaccines will continue to be monitored for rare side effects that may not be evident until millions of individuals have been inoculated.

4. How will the availability of COVID-19 vaccines affect daily life?
Even if several vaccines are authorized or approved, it will take months to manufacture and distribute enough doses of the vaccines to inoculate the general population. Estimates are that about 70% of the population needs to be immune to the infection due to either natural immunity (having prior COVID-19 infection) or vaccination to prevent spread.

There is a lot we don’t know yet that will impact when we might be able to gather again without social distancing or masks, including:

• Whether the effectiveness of vaccines under real world situations is as good as efficacy in clinical trials.
• How long immunity to COVID-19 through inoculation or prior infection will last.
• Whether vaccinations will prevent asymptomatic disease –a major factor in spread of COVID-19 – or only symptomatic disease.
• When or if enough people will be willing to receive the vaccine to achieve rates of immunity nearing 70%, given a high amount of vaccine hesitancy in the United States.

Key Takeaways
Based on what we know so far, most Americans will not be eligible to receive a vaccine until spring/summer of 2021 unless they fall into a group at high risk due to occupation, age, or comorbid conditions. There is a high likelihood that several vaccines will become available, and possible that some may be more effective in different segments of the population.

Despite how rapidly the vaccines have been developed, the FDA believes that they will have sufficient data to assure that the vaccines are safe. Public health officials advise that we remain vigilant in social-distancing and wearing masks for now, particularly over the holidays and during the winter months.

Sources
1https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations-process.html
2https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa1425/5908283