Vaccination against COVID-19 hospitalization with the 2-dose Moderna vaccine has been shown to be highly effective by Kaiser Permanente. Nonetheless, its ability to defend against delta infection is weakened over time.
A Kaiser Permanente study published in The British Medical Journal on December 15, 2021 revealed this.
“We conducted a previous study that showed the high effectiveness of the 2-dose Moderna COVID-19 vaccine, but as the delta variant became predominant in early summer of 2021, questions arose about effectiveness against variants,” said Katia Bruxvoort, Ph.D., the study’s lead author and an adjunct scientist with the Kaiser Permanente Southern California Department of Research & Evaluation.
“This study confirmed effectiveness against all variants during the study period, although we did find a drop in effectiveness over time against delta infection, from 94% effectiveness in the first 2 months after vaccination to 80% effectiveness after 6 months. Protection against hospitalization due to the delta variant remained high at 98% effectiveness.”
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SARS-CoV-2 molecular diagnostic testing is available at Kaiser Permanente in Southern California for free to all patients who ask for it, regardless of whether they are suffering from COVID-19 symptoms.
Hospital admissions and many medical procedures are also preceded by testing. A contracted lab began sequencing whole genomes of positive SARS-CoV-2 specimens in Southern California in March 2021, both from symptomatic and asymptomatic patients.
During the study period, samples were collected from March 1 to July 27, 2021, from 8,153 people who tested positive for SARS-CoV-2. There were 91.3% of these individuals who were unvaccinated, 1.4% were recipients of 1 dose of the Moderna COVID-19 vaccine, and 7.3% were recipients of 2 doses.
5186 of the samples analyzed contained variants; 39.4% had delta variants, 27.7% had alpha variants, 11.4% had epsilon, 6.9% had gamma, 2.2% had iota, 1.4% had mu, and 11.1% had other variants. Southern California had not yet detected the omicron variant at the time of this study.
The researchers compared a group of positive and a group of negative people. Their findings were:
- Efficacy of the 2-dose Moderna COVID-19 vaccine in preventing infection by variant:
- Delta: 86.7%
- Mu: 90.4%
- Alpha: 98.4%
- Other identified variants: 96 to 98%
- COVID-19 hospitalizations associated with the delta variant were significantly reduced among people who received the 2-dose Moderna COVID-19 vaccine:
- the vaccine prevented delta hospitalizations at 97.5%
- Because no non-delta variant hospitalizations among vaccinated people have been reported, its effectiveness in preventing hospitalization has not been estimated
- Moderna COVID-19 vaccine recipients did not die in hospital after receiving both doses
- In people aged 18 to 64, two doses of Moderna COVID-19 vaccines were effective against delta infection by 87.9%, while in people 65 and older, it was 75.2%.
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“While this study provides reassuring evidence of the effectiveness of 2 doses of Moderna COVID-19 vaccine in preventing COVID-19 infection and hospitalization due to variants including delta, it also has implications for booster shots,” according to Hung Fu Tseng, PhD, a researcher with Kaiser Permanente Southern California’s Department of Research & Evaluation.
“The findings of moderately reduced vaccine effectiveness of Moderna COVID-19 vaccine overtime against delta infection supports current booster dose recommendations.”