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Vaccine View
Don Mosier, PhD, MD

The Best Vaccine is a mask.
Photo Virginia Lawrence.

The bad news is that the COVID-19 epidemic is spreading rapidly here in San Diego as well as across the nation, with some local hospitals reaching capacity in their intensive care units. The good news is that two COVID-19 vaccines have shown very promising results as their large, phase 3 trials near completion, in part because the raging epidemic has allowed protection against symptomatic infection to be discerned more rapidly.

The two vaccines are both based on messenger RNA (mRNA) that codes for the viral spike protein required for the virus to enter human cells. The BNT162 vaccine from Pfizer/BioNTech and the mRNA-1273 from Moderna both protected almost 95% of trial recipients against symptomatic virus infection (up to 50% of infections, particularly in younger subjects, are asymptomatic) and had no severe cases in any vaccine recipients. Both vaccines require two doses, and protection in the Pfizer/BioNTech trial was assessed 7 days after the second dose and 28 days after the first dose. The Moderna trial gave the second dose 29 days after the first and assessed protection 14 days later. Neither vaccine caused serious side effects, but both caused local soreness, some low-grade fever, headaches, and lethargy, much like other licensed vaccines. Both vaccine manufacturers have applied for emergency use authorization from the Food and Drug Administration which, if approved, would result in front-line medical personnel receiving shots in December.

These are the first two mRNA vaccines to have advanced this close to clinical use. Because mRNA is both unstable and subject to degradation by the enzyme RNAse, the mRNA must be protected in propriety liposome formulations (essentially encapsulated in fatty bubbles). The Pfizer/BioNTech vaccine needs to be stored in ultracold freezers (-94° F.) until just before administration. The Moderna vaccine is reported to be more stable at normal freezer temperatures and can even last a few days in a refrigerator. Scaling up vaccine production is a technical challenge, and widespread distribution of either vaccine is not expected until April or May of next year, assuming there are no delayed side effects or new evidence that immunity is short lasting. There are currently over 50 over COVID-19 vaccines in various stages of development, so it is extremely likely that other vaccine formulations will be available sometime in 2021. Astra-Zeneca reported promising results on November 23rd.

With so many of our citizens refusing to wear masks, is it probable that they may also refuse to take an effective vaccine? Current polling suggests, unfortunately, that the answer is yes. Vaccines and mask wearing have been politicized and trust in federal regulatory bodies is at an all-time low. While there now appears to be light at the end of the tunnel, it will be dim indeed unless we listen to public health professionals and trust their advice.


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