One chart shows people vaccinated with Moderna had the best protection against COVID in 2021

• A large new study from the CDC charts how the Delta variant spread through both vaccinated and unvaccinated people in New York and California last year.
• The data suggests that Moderna's vaccine provided slightly superior protection to Pfizer's, while Johnson & Johnson's shot performed the worst. 
• The study was conducted before boosters were widely available, and before Omicron emerged, making it hard to draw firm conclusions about what it means for a person's immunity now. 

New data released from the Centers for Disease Control and Prevention Wednesday suggests a clear hierarchy among the three vaccines in use in the US — at least against the Delta variant.

Moderna's COVID-19 vaccine provided the most robust protection against Delta infections, Pfizer's came in second best, and Johnson & Johnson's trailed both of them, according to a large study of more than 1.1 million adults conducted between May and November of 2021 in New York and California. The new CDC study reinforces nationwide hospital data released last year. 

But the very best immune protection against a COVID-19 infection against Delta came in the form of what's called hybrid immunity — which is a blend of prior infection and vaccination. That was true regardless of which vaccine a person had received.

It's important when looking at this data to remember that it was gathered before many vaccinated people had booster shots, which early data suggest can improve the body's memory immune response. And, it's unclear what it means at this juncture in the pandemic, when there are so many more cases of the highly-infectious Omicron variant, which is a dramatically different version of the virus than Delta.

In 2021, Moderna's vaccine took 1st place

You can see Moderna's first place status against Delta reflected in two charts, one for each state in this study. First up is New York.

• The vertical axis here measures the "estimated hazard rate" — in other words, it's showing a person's risk of getting COVID-19. This rate waxed and waned across the course of the six month study period, as cases climbed and fell.
• The top 3 lines in this graph show vaccinated people in New York without any prior COVID-19 infections (broken down by vaccine brand) had a higher hazard rate than those who had been previously infected. In this group, never-infected Moderna recipients (orange) had the best protection, then Pfizer (grey), then J&J (dark blue).
• The bottom 3 lines show vaccinated people in New York with previous COVID-19 infections (again, broken down by vaccine brand) had a lower hazard rate. In this group, Moderna (light blue) again provided the best protection, followed by Pfizer (light green), then J&J (yellow). 

It's possible that the reason Moderna's vaccine provides slightly stronger immunity than the other two vaccines did is because it contains a higher dosage of mRNA than Pfizer's (100 µg compared to 30 µg per dose). It is also two doses, compared to J&J's single shot.

Moderna's two doses are also spaced one week further apart than Pfizer jabs, potentially providing a little more time for the body to mount a more robust immune response.

You can see how in California (below), much like in New York, vaccinated and previously infected people had better immune protection against Delta overall than vaccinated people who'd never contracted the virus. Once again, in both categories, Moderna's vaccine provided the best protection.

Important context for reading these graphs

1. Experts caution reading too much into these 2021 trends. It's possible that the long-term immunity people get from each vaccine brand will change over time, especially with both more variants and more shots in the mix.
2. These data are measuring the protection people with vaccines have against testing positive for COVID-19 — even with an asymptomatic infection. Vaccinated people, overall, reduce their risk of hospitalization 13 times over and reduce their risk of death 14-fold, compared to unvaccinated people.
3. This study didn't measure the severity of the COVID-19 cases people contracted. ER doctors say, by and large, the patients they are seeing with severe, life-threatening COVID cases are unvaccinated.
4. Given the life-threatening complications that COVID-19 infections can spur, including long COVID, MIS-C, and serious heart issues, the CDC continues to stress that vaccination is the wisest, safest way to deliberately develop immune protection against this virus.

"COVID vaccination helps protect by creating an antibody response without a person having to experience severe illness and death," CDC epidemiologist Benjamin Silk told reporters Wednesday, shortly before this new report was released. 

"Vaccines continue to reduce a person's risk of contracting the virus that causes COVID-19, and are highly effective at preventing severe illness. And that's why CDC recommends that everyone remain up to date on their COVID vaccination, regardless of previous infections."