They pointed to several incidents that have happened in recent weeks, as well as members of the population still hesitant to get vaccinated.
Officials say a birthday party took place in June with about 50 attendees resulted in 16 confirmed cases in the subsequent week.
The birthday party started outdoors and then moved indoors, and experts said the unvaccinated attendees were four times as likely to test positive than those who were vaccinated, with a total of six cases among 33 fully or partially vaccinated attendees and 10 cases among 13 unvaccinated attendees.
Four cases were hospitalized as a result.
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A summer camp of about 50 campers and about 20 staff members experienced a COVID-19 outbreak in July, with 13 identified cases among campers.
All staff have been vaccinated, and no cases have been identified among staff.
The campers are 11 to 14 years of age, and their vaccination status is unknown.
Additionally, 28 Connecticut residents have been identified as COVID-19 cases associated with an outbreak in Massachusetts, having traveled to Provincetown or having had contact with a case that traveled to Provincetown in July.
Officials said 93% of the cases were fully vaccinated. None of the cases required hospitalization.
The health department is taking the opportunity to remind Connecticut residents that social gatherings with a mix of vaccinated and unvaccinated should be outdoors, and indoor gatherings should include masks.
Unvaccinated children are susceptible to COVID-19 and should get vaccinated before school starts, if they are eligible.
Vaccinated and unvaccinated individuals remain at high risk for complications from COVID-19, including those with compromised immune systems, diabetes, asthma, other lung diseases, pregnancy, or obesity.
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They should consider avoiding large indoor gatherings that may include a mix of vaccinated and unvaccinated individuals.
Vaccination remains the most important defense against illness and hospitalization from COVID-19. So-called "vaccine breakthrough" cases have occurred in Connecticut, but they remain rare.
Most hospitalizations and deaths in Connecticut -- and around the country -- are in unvaccinated individuals.
Health officials strongly recommend that unvaccinated individuals get vaccinated as soon as possible to help stop the ongoing spread of the delta variant.
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