With the omicron COVID-19 variant spreading in the Bay Area and a possible fifth-wave surge of cases on the horizon, residents in Santa Clara and San Mateo counties are flocking to get booster shots. In Mountain View, Palo Alto and Los Altos, 41% of eligible residents have received the boosters, according to Santa Clara County.

Public health leaders in both counties say they've also seen a good start on vaccinations of children ages 5 to 11, the latest eligible group, but they want to push harder to get children in that age group inoculated.

Santa Clara County began administering the Pfizer-BioNTech vaccine to the 5 to 11 year olds on Nov. 3, the day after the Centers for Disease Control and Prevention (CDC) approved emergency use authorization. The pediatric dosage is one-third of that given to adults.

As of Wednesday, 39% of children in that group have been vaccinated with at least one shot, according to county data. Half of those 65,938 children have been fully vaccinated, state data shows.

But in Santa Clara County, vaccinations of 5 to 11 year olds have plateaued, Dr. Ahmad Kamal, Santa Clara County's COVID-19 director of health care preparedness, told the Board of Supervisors on Tuesday. Kamal said the county is partnering with the Office of Education to run more clinics, looking to offer more after-school appointments and will redistribute pediatric vaccines to locations where they've seen the most demand.

There is room for hope that the number of children who will be vaccinated will rise. After a slow start and concerns by parents regarding the vaccine's safety, a whopping 92.3% of children in the next youngest age group, 12- to-17-year-olds, have been vaccinated, according to county data.

San Mateo County shows a similar trajectory. Louise Rogers, chief of the San Mateo County Health System, said Tuesday that 38% of eligible children ages 5 to 11 have received their first shots and she is encouraged the number will continue to rise.

Both counties have already slightly surpassed what is projected to be the national average for pediatric vaccination. A recent Kaiser Foundation study found nationally only one-third of parents planned to seek to have their children inoculated against the coronavirus, Rogers said during a San Mateo County Board of Supervisors meeting.

Her department is heartened by the initial turnout, and she hopes the rate will continue to ramp up as more clinics become available, she said. The health department is working in partnership with the San Mateo County Office of Education to establish vaccination sites in 13 school locations.

Dr. Anand Chabra, San Mateo County's COVID-19 mass vaccination section chief, said the county would have a fuller picture of vaccination rates for children ages 5 to 11 next week.

The county health department will continue to push for greater public education to help parents understand that the vaccines are safe and necessary, particularly in light of the recent appearance of the omicron variant. Omicron is thought to be more transmissible than previous variants, including the ubiquitous delta strain, but it isn't yet known if it causes more severe infection, Rogers said.

Dr. Sara Cody, Santa Clara County's health officer, said that cases are again rising in what could turn into a fifth wave of the virus. The seven-day rolling average of cases has picked up, increasing from 165 on Nov. 26 to 195 on Dec. 8, according to county data. Data related to the Thanksgiving holiday, when many families gathered, isn't yet available to see how big the spike might be, she said.

Santa Clara County's health department is also seeing an increase in DNA fragments of the SARS-CoV-2 virus, the scientific name for the coronavirus, in wastewater, another sign of growing infections in the community, Cody said.

Lately, both Santa Clara and San Mateo counties have wrestled with logistical snafus that have frustrated some vaccine seekers.

Santa Clara County Supervisor Joe Simitian said he tried to unsuccessfully book a booster appointment at the county's Mountain View vaccine clinic site. He'd heard from constituents that no appointments were available within a few hours after appointment dates were released.

"The hard fact of the matter is we've got demand that is not being met," Simitian said, even if there is plenty of supply. He pressed staff to push the county's vaccine partners, such as Palo Alto Medical Foundation, to offer more appointments.

Simitian said he's concerned that a failure to provide rapid appointments will turn people away from the very thing the county says is most important to stemming the COVID-19 outbreak. Community members have told him they are "COVID fatigued"; the desire to get the boosters is starting to wane, he said.

"You're not going to get the same level of cooperation," he said as with the initial round of vaccinations.

To remedy the situation, Kamal said in the past two weeks that Santa Clara County has added 2,000 more booster appointment slots per day. The county will allow appointment booking 17 days in advance at sites where slots fill up quickly. They'll also re-distribute pediatric-versus-booster shots based on demand, such as giving boosters earlier in the day and scheduling pediatric slots after school hours and weekends. Disaster service workers and other county staff will also be tapped to help administer the shots.

San Mateo County has had similar logistical issues. The health department canceled a vaccine clinic at the San Mateo Medical Center on Dec. 6 due to a staffing shortage, and "strongly recommend" making an appointment in advance at myturn.ca.gov, the department stated on Twitter. Only a limited number of people without appointments will be able to be vaccinated.

Rogers had a message for the public when it comes to COVID-19 vaccination: Keep up the momentum. It's important for everyone who is eligible to be fully vaccinated, she said, and to get their boosters to ride out the wave of the coming omicron variant.

"This is a time when we find ourselves needing resilience and stamina," she said.