Wait, did I hear more good vaccine news? Is this too good to be true?!


A: Another Monday, another ray of light breaking through the COVID-19 storm cloud.

The news is good, but we must still BE PATIENT and HUNKER DOWN for the winter.

Fresh on the heels of the happy Pfizer/BioNTech news from last week, Moderna announced an efficacy of *94.5%* in the first look at data from the clinical trial of its similar mRNA vaccine.

What does “efficacy” mean? Vaccine efficacy is interpreted very narrowly as the % reduction in disease among the vaccinated compared to placebo group in the trial.

So, for example, if there were half as many infections in the vaccine group as in the placebo (say 50 compared to 100), the efficacy would be 50%.

In this trial, out of 30,000 participants in the trial, half were given the vaccine and half a saline placebo.

So far, 95 participants contracted COVID-19;

🔥 90 in the placebo group and

🔥 5 in the vaccine group

If the vaccine had zero efficacy, we would have expected a similar number of cases in the vaccine and placebo groups (~90 cases in both groups). Since there were only 5 cases in the vaccine group, this was 85 fewer cases than “expected” if the vaccine did not work.

So how well does it work? The % reduction in the vaccine group compared to the placebo group was 85/90= 94.45%

Is this good news? Heck yeah! This number is even higher than the surprisingly good efficacy number from Pfizer last week of 90%. Since Pfizer and Moderna both use an mRNA vaccine technology, it makes sense that they are seeing similar efficacy. This also continues to bode well in principle for other vaccine approaches that target the same SARS-CoV-2 spike protein.

💡What more did we learn from the Moderna compared to Pfizer results?

➡️ The Moderna trial had 11 cases of severe COVID-19 among the placebo group and none among the vaccine group, allowing them to more confidently say that the vaccine also protects against severe disease (The Pfizer trial did not have any severe cases in either group).

➡️ Moderna announced that its vaccine remains stable in conventional refrigerators for a month and normal freezers for six months, meaning much easier storage than Pfizer’s vaccine which must be stored at −70 °C before delivery. This is really good news for the logistics of distribution.

❓What questions remain?

➡️ Does the vaccine work in older people and those with underlying conditions? The Moderna trial included substantial numbers of volunteers over age 65 as well as those < 65 with high risk conditions. While detailed subgroup data on the infection cases was not yet released, Moderna stated that the safety and efficacy was consistent across different demographic groups.

➡️ Does the vaccine prevent you from transmitting to others? As with the Pfizer vaccine, the Moderna primary endpoint was confirmed *symptomatic* COVID-19 cases. Since asymptomatic cases in either group were not picked up, we still don’t know whether the vaccine prevents infection completely or the ability to transmit the virus others. Some other trials are testing participants regularly and should be able to test this more directly.

➡️ How long will protection last? Since both the virus and vaccine are so new, we don’t know how long vaccine protection will last. Participants will be followed for at least two years to learn about duration of immunity.

➡️ Is the vaccine safe? No serious safety concerns were reported in either vaccine. The most serious side effects included fatigue, muscle pain, and headache. Volunteers will be followed over time for to monitor any longer-term effects.

➡️ When can I get the vaccine? For most people, Spring 2021 at the earliest (current best guess). Both Moderna and Pfizer will apply for FDA emergency use authorizations within the next few weeks, but the FDA review takes some time. The vaccine requires two doses and supplies are limited. Front-line health care workers and those at the highest risk may start to receive the vaccine in late 2020/early 2021. As supply ramps up and logistics are put into place, more of the general population should have access as 2021 unfolds. If more vaccine candidates are successful in the coming weeks/months, this should accelerate access and supply.

➡️ Does this mean I can be less careful now? NO! If anything, the news that the cavalry is on the horizon makes it even MORE important to protect yourself and prevent as much transmission as possible for the next few months. Giving up trips and gatherings for a while longer means you might be able to avoid hospitalization, death, or long-term illness from COVID-19 forever. Let’s do this!!

Those Nerdy Girls

Links to coverage of the Moderna Vaccine:

STAT news:

Science Magazine

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