Walgreens pharmacist Jessica Sahni will hold the vaccine against Pfizer BioNTech coronavirus disease (COVID-19) at the New Jewish Home in New York on December 21, 2020.

Yuki Iwamura | Reuters

Pfizer said it had fully enrolled its Covid-19 vaccine study in children ages 12-15, an important step before the vaccine could be used in that age group.

The study, an extension of the study used to support the company’s emergency approval for the vaccine in people aged 16 and over, enrolled 2,259 children between the ages of 12 and 15, Pfizer told CNBC on Friday. The entry on a government clinical trial website has been updated to determine that subjects are no longer being recruited.

The vaccine developed with German partner BioNTech was approved in December for people aged 16 and over. Studies in younger age groups are needed to ensure the correct dose as well as safety and effectiveness in these different groups, said Dr. Evan Anderson, a pediatrician at Emory University School of Medicine.

“I am very uncomfortable sending my children back to school where, despite the school’s best efforts, there is a real risk of getting Covid-19,” Anderson told CNBC in October.

While children are less affected by Covid-19 than adults, they still catch the virus and get sick. Some even died. According to a report from the American Academy of Pediatrics and the Children’s Hospital Association, more than 2.5 million cases of Covid-19 in children were reported as of Jan. 14, about 13% of all cases.

“Children can still get sick and die from Covid-19,” said Dr. Paul Offit, director of the Vaccine Education Center and an infectious disease doctor at Philadelphia Children’s Hospital. “In the past year, as many children died of Covid-19 as of influenza. And we recommend an influenza vaccine for children.”

Offit also pointed out that children can suffer from a disease related to Covid-19 called multisystem inflammatory syndrome, “which can be debilitating”.

According to the Centers for Disease Control and Prevention, as of Jan. 8, there were 1,659 cases of the syndrome in children named MIS-C and 26 related deaths. There were a total of 78 deaths from Covid-19 in children under 4 years old and 178 in children between 5 and 17 years old, according to CDC data, although those numbers do not explain all deaths from the United States

Children compete for class at PS 361 on the first day of returning to class during the coronavirus disease (COVID-19) pandemic in the Manhattan neighborhood of New York City, New York, United States, on December 7, 2020.

Carlo Allegri | Reuters

Pfizer declined to say when it expected results from the study, which would depend on the observed infection rate, to compare the rates in the placebo group with those who received the vaccine. With infection rates higher in the US since the fall – the 7-day average of daily cases now stands at 187,500, according to a CNBC analysis of the Johns Hopkins University data – vaccine effectiveness studies have shown their ads are getting faster.

However, enrollment for adolescent studies has been slower than hoped, at least for Moderna’s study in children ages 12-17, Moncef Slaoui, chief advisor to Operation Warp Speed, the Trump administration’s vaccine effort, said at their last meeting on Dec. January.

By then, around 800 children had been included in the study for over a month, of which around 3,000 were needed. Moderna’s vaccine was approved for people aged 18 and over in December, weeks after its teenage study began. Pfizer lowered the age of his trial to 12 years in October.

“While enrollment was lower during the holiday season, we expect an increase in the new year as planned,” said Moderna spokeswoman Colleen Hussey on Friday. “We are on track to provide updated data by mid-2021.”

AstraZeneca, whose vaccine developed by Oxford University is in late-stage trials in the US and approved in the UK, told CNBC Friday that it plans to continue UK trials in a new protocol for children ages 5-18 from the coming months. “”

Johnson & Johnson, whose results are expected in the third phase in adults, said it was in talks with regulators about including pediatric populations in its development plan. The same technology used for the Covid-19 vaccine was found to have been used in vaccines given to more than 200,000 people, including people over 65, infants, children, HIV-positive adults, and pregnant women .

Typically, vaccine trials are conducted in younger age groups after they have been shown to be safe and effective in older groups. The manufacturers of Covid-19 vaccines have indicated that they will follow this plan here as well.

Moderna’s chief executive Stephane Bancel said earlier this month the company is unlikely to have data on children ages 11 and younger who would include a lower dose before next year. He said he expected data for children 12 years and older could be available before September.

U.S. public health officials such as White House Chief Medical Officer Dr. Anthony Fauci, said they hope that by fall 75% to 80% of the US population could be vaccinated so life can return to some form of normal.

About 78% of the US population, or 255 million people, are over 18 years old, according to a CNBC analysis of the census data. Another 25 million people are between 12 and 17 years old.

Fauci did not immediately respond to a query about the need to include children in vaccinations in order to meet his goal of 75% to 80% coverage.

“It is important that all children are vaccinated, and manufacturers cannot conduct these trials fast enough,” Angela Rasmussen, virologist and subsidiary at the Georgetown Center for Global Health Science and Safety, told CNBC on Friday. “The more people of all ages are vaccinated, the better.”