Varicella, commonly known as chickenpox, manifests as an itchy rash and spreads through airborne, droplet, and contact transmission. Though typically mild-to-moderate, it can result in severe complications like pneumonia and even death. In October 2022, the NYC Department of Health, and Mental Hygiene (DOHMH) detected a varicella outbreak, mainly impacting migrants from or passing through Central and South America, residing in shelters or residential facilities within NYC. As of March 8, 2024, 873 varicella cases linked to the outbreak have been reported.
Most cases (53.0%) were observed among children and adolescents aged 4–18 years, with a striking 91.9% lacking documented varicella vaccination at the onset of symptoms. Hospitalizations related to varicella totaled 28, with no reported fatalities. Of the cases with a known transmission source (89.3%), shelters and residential facilities (41.3%) and importation or potential importation (39.4%) emerged as the most prevalent sources. School-based transmission constituted a mere 1.2% of cases. 1
Main Takeaways
- NYC is experiencing a notable varicella outbreak primarily affecting migrant populations from Central and South America, with over 870 reported cases since October 2022.
- 91.9% of cases lacked documented varicella vaccination at symptom onset, emphasizing the importance of maintaining high vaccination rates, especially among children and adolescents.
- The outbreak highlights the need for implementing preventive measures, such as vaccination campaigns and temporary closures of affected facilities, to control transmission, particularly in vulnerable settings like shelters and residential facilities.
According to the CDC, “2 doses of varicella vaccine for children, adolescents, and adults to protect against varicella. Children are routinely recommended to receive the first dose at age 12 through 15 months and the second dose at age 4 through 6 years old.”2
Around 27,000 doses of varicella-containing vaccines were given to newly arrived migrant populations by vaccination teams dispatched by the DOHMH and NYC’s public hospital system.
“In countries that do include varicella vaccination in routine immunization schedules, vaccination programs might have been limited or disrupted because of multiple factors,” according to the investigators. “Countries of origin were primarily tropical countries where varicella susceptibility among adults is higher; limited published data indicate a lower varicella seroprevalence among young adults than that reported in the US. Many persons who recently migrated to NYC currently live in residential facilities, some are actual congregate settings, and substantial varicella transmission has been reported in one residential facility with private rooms.”1
Institutions such as city-run shelters, residential facilities, schools, and healthcare facilities reported suspected varicella cases to the DOHMH. Investigations entailed patient interviews and the scrutiny of medical and immunization documentation. Cases were categorized as outbreak-associated if they displayed a rash clinically consistent with varicella and either received a diagnosis from a healthcare provider or had known contact with the virus. This is important to maintain safety in NYC.
Investigators reiterate, “New York State law requiring documentation of 2 doses of varicella vaccine to attend school grades K–12 (9). In NYC, varicella vaccine coverage among kindergarten children during the 2021–22 school year was 96.7%”1
In summary, this outbreak underscores the necessity of maintaining high varicella vaccination rates to control transmission, especially in vulnerable settings like shelters and residential facilities. Prioritizing vaccination efforts and reinforcing preventive measures are essential to combat varicella outbreaks and protect public health effectively.
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