Effectiveness of Covid-19 Vaccines over a 9-Month Period in North Carolina
New England Journal of Medicine·
- DOI
- 10.1056/nejmoa2117128
- PMID
- 35020982
- PMCID
- PMC8781317
- OpenAlex
- W4206354262
- Study type
- Journal article
- Publisher
- Massachusetts Medical Society
- Article type
- journal-article
- Integrity
- current
Why this research matters now
The findings demonstrate that waning protection against infection resulted from both declining immunity over time and delta variant emergence, informing decisions about booster timing and vaccine policy. All three vaccines showed durable effectiveness in preventing severe outcomes (hospitalization and death), supporting continued vaccination efforts.
Structured evidence summary
Research question
The study examined the duration of protection provided by three COVID-19 vaccines in North Carolina and sought to determine whether increased postvaccination infections during summer 2021 resulted from waning immunity, the delta variant emergence, or both.
Study design
This was a retrospective cohort study using linked surveillance and vaccine registry data covering approximately 10.6 million North Carolina residents over nine months (December 2020 to September 2021). Cox regression models estimated vaccine effectiveness against infection, hospitalization, and death as a function of time since vaccination.
Population and setting
The study population comprised approximately 10.6 million residents of North Carolina who received BNT162b2, mRNA-1273, or Ad26.COV2.S vaccines between December 11, 2020, and September 8, 2021.
Main findings
Effectiveness against COVID-19 infection declined over time for all three vaccines: BNT162b2 dropped from 94.5% at 2 months to 66.6% at 7 months, mRNA-1273 from 95.9% to 80.3%, and Ad26.COV2.S from 74.8% at 1 month to 59.4% at 5 months. The two mRNA vaccines showed effectiveness declines of approximately 10-15 percentage points from mid-June to mid-July when delta became dominant. All three vaccines maintained stronger effectiveness against hospitalization and death than against infection, with the two mRNA vaccines providing higher protection levels than Ad26.COV2.S.
Public-health relevance
The findings demonstrate that waning protection against infection resulted from both declining immunity over time and delta variant emergence, informing decisions about booster timing and vaccine policy. All three vaccines showed durable effectiveness in preventing severe outcomes (hospitalization and death), supporting continued vaccination efforts.
Important limitations
This summary relies on the supplied single-article abstract and metadata. Full interpretation of study limitations, including potential confounding, generalizability beyond North Carolina, and detailed methodological constraints, requires review of the complete published article.
GIDS interpretation
This article would be discoverable through GIDS queries for vaccine effectiveness studies, COVID-19 surveillance data from the United States, and research on waning immunity or delta variant impact. The classifier links to surveillance, vaccination, and vaccine effectiveness topics support retrieval in monitoring workflows focused on vaccine performance assessment.
Related GIDS surveillance
Literature context does not validate, explain, or change a surveillance signal. Exact and contextual relationships are shown separately.
Evidence relationships
This article has 11 auditable classifier relationships to diseases, places, topics, and study design.