By Shereen Siewert

Health officials on Tuesday urged all residents, including people who are fully vaccinated, to wear a mask in public indoor settings as Marathon County experiences substantial community transmission of COVID-19.

The recommendation, from the Centers for Disease Control and Prevention (CDC) and the WI Department of Health Services (DHS), comes alongside a rising number of new COVID-19 cases globally and growing concern about highly transmissible strains like the delta variant. And reports of fully vaccinated people testing positive for COVID-19 are also increasing, though health officials say the bottom line is that the existing COVID-19 vaccines are still very good at preventing symptomatic infections. Less than .001% of those fully vaccinated have experienced a fatal breakthrough case, while fewer than .004% of those fully vaccinated had to be hospitalized.

In a news release, Marathon County Public Health Information Officer Aaron Ruff said health officials are now recommending all teachers, staff, students and visitors of K-12 schools wear a mask indoors regardless of vaccination status.

Marathon County Health Officer Joan Theurer said the combination of masks and vaccines are the “best combination to stop the spread.”

CDC recommends fully vaccinated people who have a known exposure to someone with suspected or confirmed COVID-19 be tested 3-5 days after exposure, and wear a mask in public indoor settings for 14 days or until they receive a negative test result.

These recommendations are based on new science which indicates the Delta variant is highly infectious and is spreading more quickly than any other strains of COVID-19.  

Infections in fully vaccinated people happen in only a small proportion of people who are fully vaccinated, even with the Delta variant.  As of July 22, among those fully vaccinated in Wisconsin, 0.1% have become infected with COVD-19. Most people who experience infection after being fully vaccinated report mild or no symptoms.

Past infection with COVID-19 does not assure protection from the Delta variant, health officials say, and no vaccine is 100 percent effective. Dr. Jonas Salk’s polio vaccine, for example, was 80%-90% effective in preventing paralytic disease while the efficacy of the measles vaccine was 94% among a highly vaccinated population during large outbreaks.

Clinical trials found the vaccines from Pfizer and Moderna 94%–95% effective at preventing symptomatic COVID-19 – a figure much higher than initially hoped.

Breakthrough infections

Even among vaccinated people, breakthrough infections can happen. From members of the Milwaukee Brewers to athletes in the Olympics to Republican U.S. Senator Lindsey Graham, those cases are making headlines.

Breakthrough infections are happening more frequently than previously expected. Health officials attribute the numbers to the growing dominance of the delta variant. Still, infections in vaccinated people are still very rare and usually cause mild or no symptoms.

For example, 46 U.S. states and territories reported 10,262 breakthrough infections to the CDC between Jan. 1 and April 30, 2021. By comparison, there were 11.8 million COVID-19 diagnoses in total during the same period.

When a vaccine is 95% effective, that does not mean that the shot only protects 95% of people who receive it while the remaining 5% will contract COVID. Rather, effectiveness of a vaccine is a measure of relative risk.

Notably, 27% of breakthrough cases reported to the CDC were asymptomatic. Only 10% of the breakthrough-infected people were hospitalized and 2% died. By comparison, last spring, when vaccines were not yet available, over 6% of confirmed infections were fatal.

Mask wearing, social distancing and other steps to stop COVID-19 have also curtailed influenza this year, health officials say, and drug manufacturers reported a sharp drop in sales of cold and flu-related remedies. The reason, epidemiologists think, is that the public health measures taken to keep the coronavirus from spreading—notably mask wearing and social distancing—also stop the flu, writes Scientific American. Influenza viruses are transmitted much the same way as SARS-CoV-2, the virus that causes COVID-19, and they are less effective at jumping from person to person.

The Marathon County Health Department’s recommendation is almost certain to prompt sharp debate among school districts determining whether to impose mandatory mask rules for the upcoming school year. So far, Wausau has no plans to change the district’s “masks optional” rule for fall, Wausau Pilot & Review previously reported.

For information on where to get a vaccine go to Marathon County COVID-19 Vaccine webpage or vaccines.gov.