Transmission from vaccinated individuals in a large SARS-CoV-2 Delta variant outbreak.

An outbreak of over 1,000 COVID-19 cases in Provincetown, Massachusetts (MA), in July 2021-the first large outbreak mostly in vaccinated individuals in the US-prompted a comprehensive public health response, motivating changes to national masking recommendations and raising questions about infection and transmission among vaccinated individuals. To address these questions, we combined viral genomic and epidemiological data from 467 individuals, including 40% of outbreak-associated cases. The Delta variant accounted for 99% of cases in this dataset; it was introduced from at least 40 sources, but 83% of cases derived from a single source, likely through transmission across multiple settings over a short time rather than a single event. Genomic and epidemiological data supported multiple transmissions of Delta from and between fully vaccinated individuals. However, despite its magnitude, the outbreak had limited onward impact in MA and the US overall, likely due to high vaccination rates and a robust public health response.

Inequities in COVID-19 Vaccination Coverage Among Pregnant Persons, by Disaggregated Race and Ethnicity - Massachusetts, May 2021-October 2022.

National estimates suggest that COVID-19 vaccination coverage among pregnant persons is lower among those identifying as Hispanic or Latino (Hispanic) and non-Hispanic Black or African American. When examining COVID-19 vaccination coverage during pregnancy by race and ethnicity, however, data are typically limited to large, aggregate categories that might obscure within-group inequities. To address this, Massachusetts examined COVID-19 vaccination coverage among pregnant persons by combinations of 12 racial and 34 ethnic groupings. Among 102,275 persons with a live birth in Massachusetts during May 1, 2021-October 31, 2022, receipt of ≥1 dose of a COVID-19 vaccine before or during pregnancy was 41.6% overall and was highest among persons who identified as Asian (55.0%) and lowest among those who identified as Hispanic (26.7%). However, within all broad racial and ethnic groupings, disparities in COVID-19 vaccination coverage were identified when the data were disaggregated into more granular categories; for example, COVID-19 vaccination coverage ranged from 10.8%-61.1% among pregnant persons who identified as Hispanic. Disaggregated analyses reveal diverse experiences within broad racial and ethnic groupings. This information can be used to guide outreach to pregnant persons in communities with lower rates of COVID-19 vaccination coverage during pregnancy.

Characteristics of People With and Without Laboratory-Confirmed SARS-CoV-2 Infection During Pregnancy, Massachusetts, March 2020-March 2021.

OBJECTIVES: Pregnant people infected with SARS-CoV-2, the virus that causes COVID-19, are at increased risk for severe illness and death compared with nonpregnant people. However, population-based information comparing characteristics of people with and without laboratory-confirmed SARS-CoV-2 infection during pregnancy is limited. We compared the characteristics of people with and without SARS-CoV-2 infection during pregnancy in Massachusetts. METHODS: We compared maternal demographic characteristics, pre-pregnancy conditions, and pregnancy complications of people with and without SARS-CoV-2 infection during pregnancy with completed pregnancies resulting in a live birth in Massachusetts during March 1, 2020-March 31, 2021. We tested for significant differences in the distribution of characteristics of pregnant people by SARS-CoV-2 infection status overall and stratified by race and ethnicity. We used modified Poisson regression analyses to examine the association between race and ethnicity and SARS-CoV-2 infection during pregnancy. RESULTS: Of 69 960 completed pregnancies identified during the study period, 3119 (4.5%) had laboratory-confirmed SARS-CoV-2 infection during pregnancy. Risk for SARS-CoV-2 infection was higher among Hispanic (adjusted risk ratio [aRR] = 2.3; 95% CI, 2.1-2.6) and non-Hispanic Black (aRR = 1.9; 95% CI, 1.7-2.1) pregnant people compared with non-Hispanic White pregnant people. CONCLUSIONS: This study demonstrates the disproportionate impact of SARS-CoV-2 infection on Hispanic and non-Hispanic Black pregnant people in Massachusetts, which may widen existent inequities in maternal morbidity and mortality. Future research is needed to elucidate the structural factors leading to these inequities.

Evidence of transmission from fully vaccinated individuals in a large outbreak of the SARS-CoV-2 Delta variant in Provincetown, Massachusetts.

Multiple summer events, including large indoor gatherings, in Provincetown, Massachusetts (MA), in July 2021 contributed to an outbreak of over one thousand COVID-19 cases among residents and visitors. Most cases were fully vaccinated, many of whom were also symptomatic, prompting a comprehensive public health response, motivating changes to national masking recommendations, and raising questions about infection and transmission among vaccinated individuals. To characterize the outbreak and the viral population underlying it, we combined genomic and epidemiological data from 467 individuals, including 40% of known outbreak-associated cases. The Delta variant accounted for 99% of sequenced outbreak-associated cases. Phylogenetic analysis suggests over 40 sources of Delta in the dataset, with one responsible for a single cluster containing 83% of outbreak-associated genomes. This cluster was likely not the result of extensive spread at a single site, but rather transmission from a common source across multiple settings over a short time. Genomic and epidemiological data combined provide strong support for 25 transmission events from, including many between, fully vaccinated individuals; genomic data alone provides evidence for an additional 64. Together, genomic epidemiology provides a high-resolution picture of the Provincetown outbreak, revealing multiple cases of transmission of Delta from fully vaccinated individuals. However, despite its magnitude, the outbreak was restricted in its onward impact in MA and the US, likely due to high vaccination rates and a robust public health response.