San Diego County officials said an area around 60 homes in Vista will be treated.
Vaccines made with novel adjuvants are more reactive than those without adjuvants.
Black patients were overrepresented as 37% of the patient population.
A letter emphasizing the benefits of vaccination for cardiac health was most effective.
The United States is using three-strain flu vaccines with the same components as those used in Southern Hemisphere vaccines.
The WHO recommends manufacturers produce trivalent (three-strain) vaccines for use in the 2025 Southern Hemisphere influenza season.
Among adults for whom RSV vaccines are recommended, 21% say they will definitely get vaccinated this upcoming season.
Through a third-party pharmacy, people interested in the self or caregiver option will complete a screening and eligibility assessment when they order the vaccine.
Most of the kids who died were unvaccinated, and about half had no underlying health conditions.
The findings come on the cusp of the Northern Hemisphere flu and respiratory syncytial virus seasons and rising US COVID-19 cases.
