7 things to know about COVID-19 vaccines

Enthusiasm surrounding COVID-19 vaccines is on the upswing after Pfizer (NYSE:PFE) and Moderna (NSDQ:MRNA) announced preliminary data suggesting their vaccines could be more than 90% effective at preventing COVID-19 infections.

Health and Human Services (HHS) Secretary Alex Azar said today in an NBC interview that he believes a COVID-19 vaccine would be available to the general public by the spring of 2021.

The Bay Area Council hosted a webinar yesterday to provide more information about coronavirus vaccines. Here are seven considerations to keep in mind now that the prospect of a widely deployed COVID-19 vaccine seems tangible — at least in 2021:

1. COVID-19 vaccines are the most anticipated since at least the 1950s

“The COVID vaccine is clearly the most anticipated vaccine since polio,” said Dr. Jeffrey Silvers, medical director of pharmacy and infection control at Sutter Health, referring to the inactivated poliovirus vaccine introduced in the early 1950s.

While it took less than a year to develop promising COVID-19 vaccines, foundational polio vaccine research started in the 1930s or even earlier. “With the polio vaccine, they started the work 25 years before it was finally released,” Silvers said in the webinar.

2. Most COVID-19 vaccine candidates require two doses

Johnson & Johnson is unique. The company is exploring both one- and two-dose regimens for its JNJ-78436725 COVID-19 vaccine candidate. The other six vaccines that are part of the Operation Warp Speed require two vaccine doses. “It’s important to note. They are not interchangeable,” Silvers said. “If you get one dose of the Moderna vaccine, you cannot get one dose of Pfizer. You have to get two of the same vaccine.”

It is worth keeping this fact in mind when looking at the total number of doses of COVID-19 vaccines (see below). Calculating the number of vaccinated patients generally requires dividing the doses in two.

3. ‘Severe’ COVID-19 vaccine shortages are likely initially

In August, the U.S. government inked a deal with six COVID-19 vaccine candidate makers to provide 500 million doses once they win the regulatory go-ahead. More recently, Pfizer has announced plans to produce up to 50 million vaccine doses this year and as many as 1.3 billion doses in 2021. Moderna hopes to have 20 million doses by the end of 2020 and at least 500 million doses next year. At least some of those doses will be distributed abroad. Less than 5% of the world’s population lives in the U.S.

“You can imagine, at least at the onset, there will be a severe shortage,” said Dr. Bernard Lo, director of the University of California, San Francisco’s Program in Medical Ethics.

Even the prospect of vaccinating essential workers could prove daunting, considering that some 55 million people fall under that category.

Rationing will be a necessity initially, Lo said. Potential candidates to receive the first doses of the vaccine include nursing home residents and workers and home health aides. Many healthcare employees, including doctors, nurses, nurse aides, respiratory techs and first responders are also natural candidates to be early recipients of a COVID-19 vaccine.

That said, a substantial number of people in the United States are wary about receiving a COVID-19 vaccine. A September survey published in USA Today revealed that two-thirds of Americans wouldn’t take a vaccine when it is first available. An October CNN survey revealed that just over half of Americans would take a vaccine if it were “widely available at a low cost.”

4. FDA requires COVID-19 vaccines to have a 50% or higher efficacy rate

To approve a vaccine, the FDA requires COVID-19 vaccine candidates to prevent or at least lessen the severity of infections in at least half of the patients receiving it in a placebo-controlled trial.

Pfizer claims its COVID-19 could have an efficacy of around 90%.

The agency also requires monitoring clinical trial volunteers for at least two months after receiving the last vaccine dose for emergency use authorization. For full approval, FDA requires six months’ worth of safety data.

5. Injectable COVID-19 vaccines may not produce mucosal immunity

Injectable COVID-19 vaccines will produce immunoglobulin G (IgG) antibodies, which are found in the blood and other body fluids. Such vaccines are less likely to result in IgA antibodies, which are found in the respiratory tract and digestive system.

“It’s important to note that immunity of the airways, the nose and the mouth are mostly [a result of] IgA,” Silvers said. While IgG antibodies will protect the host, “some people may conceivably still carry the [SARS-COV-2] virus or even be able to transmit the virus,” he added.

Health experts thus urge the public to wear masks after vaccines are widely available.

A number of researchers, however, are working on a variety of nasal-based strategies to fight COVID-19 infections, including nasal delivery of vaccines and a nasal spray that blocks absorption of the virus.

6. COVID-19 vaccine side effects will likely be common, but mild

Side effects for the COVID-19 vaccine are “likely to be fairly common,” Dr. Lo said. Researchers have not linked severe side effects to COVID-19 vaccines, but they have observed side effects such as localized aching and fever. The rate of side effects is “higher than with the flu vaccine,” Lo said. “About 10% of people who get flu vaccines get side effects with about 2–3% getting fevers.”

7. Durability of COVID-19 immunity is still a wild card

Researchers have identified several reported cases of SARS-CoV2 reinfections, including cases in Ecuador, Hong Kong, Belgium, the Netherlands, India and the United States.

“Implications of reinfection are unclear,” concluded a recent briefing note from UBS. But factors that are likely pertinent include the initial viral dose, potential exposure to multiple COVID-19 strains and changes in a person’s general health.

That said, signs are promising that COVID-19 vaccines could produce immunity lasting at least multiple months. A study published in Cell suggests that immunity could last 5–7 months. If this proves to be the case, COVID-19 boosters will likely be necessary.

This article has been updated with comments from U.S. Department of Health and Human Services secretary Alex Azar.