Except for some Jersey Shore towns, most of region not impacted by revised CDC mask guidelines

Philly already has recommended indoor usage for vaccinated people despite moderate COVID-19 transmission levels

If you're taking a Jersey Shore vacation in the near future, you may need to bring a mask — even if you're fully vaccinated against COVID-19.

Updated guidance from the U.S. Centers for Disease Control and Prevention recommends everyone wear masks indoors, regardless of vaccination status, in counties that are reporting high or substantial transmission of the coronavirus. 

Philadelphia and its surrounding counties, including those in South Jersey, are only reporting moderate transmission and are currently unaffected by the guidance, though Philly is strongly urging all residents to wear masks indoors. But the new guidance could impact people headed to the shore. 

Atlantic and Ocean counties have substantial transmission and Monmouth County has high transmission, CDC data show. Cape May County — which includes Ocean City, the Wildwoods and Cape May — is not impacted by the guidance because it only has moderate transmission. 

The CDC also is recommending anyone who enters a school building wear a face mask, a policy the School District of Philadelphia already has adopted for the upcoming academic year. 

The CDC guidelines serve as recommendations, but state and local governments can mandate them as they see fit. The CDC update comes as the highly contagious Delta variant has become the dominant coronavirus version in the United States, accounting for more than 80% of the country's new cases.

Vaccines still provide substantial protection against the Delta variant, CDC officials. But when vaccinated people develop symptomatic COVID-19, they can transmit the virus. 

"Getting vaccinated continues to prevent severe illness, hospitalization and death — even with Delta," CDC Director Dr. Rochelle Walensky said. "It also helps reduce the spread of the virus in our communities. 

"Vaccinated individuals continue to represent a very small amount of transmission occurring around the country. We continue to estimate that the risk of a breakthrough infection with symptoms upon exposure to the Delta variant is reduced by sevenfold. The reduction is twentyfold for hospitalizations and death." 

Though Philadelphia falls shy of the CDC criteria, health officials last week recommended vaccinated residents wear masks indoors, citing a "disturbing increase in hospitalizations due to COVID-19 among children." 

"Not everyone will do it, we know that, but if enough people do combined with our high vaccination rate, we hope to be able to head this off," Jim Garrow, a spokesperson for the Philadelphia Department of Public Health, said last week. "If things continue to get worse, we may consider moving to a more strict mandate."

Five Pennsylvania counties and seven New Jersey counties meet the criteria for the CDC's new masking guideline.

In Pennsylvania, Cameron and Crawford counties have high transmission. Adams, Monroe and Wyoming counties have substantial transmission. As of Tuesday, the Pennsylvania Department of Health reported 5.8 million residents had received at least one dose of a COVID-19 vaccine and 5.6 million residents were fully vaccinated.

In New Jersey, Atlantic, Bergen, Essex, Ocean, Middlesex and Passaic have substantial transmission. Monmouth County has high transmission. As of Tuesday, health officials reported 5.6 million residents had received at least one dose and 5.2 million residents were completely inoculated.

Three months after the CDC said fully vaccinated people do not have to wear masks outdoors — and a little more than two months after it lifted an indoor mask recommendation — data show 46% of counties nationwide reporting high COVID-19 transmission rates and 17% reporting substantial transmission.