People receive their second COVID-19 boosters in Waterford, Michigan
A nurse fills up syringes with the coronavirus disease (COVID-19) vaccines for residents who are over 50 years old and immunocompromised and are eligible to receive their second booster shots in Waterford, Michigan, U.S., April 8, 2022. Reuters

The White House expects the rate of vaccination in its fall booster campaign to pick up over the coming weeks, and its COVID response coordinator Dr. Ashish Jha on Friday characterized the initial pace as "a really good start."

The United States in September started rolling out the updated COVID shots, redesigned to take on both the currently circulating BA.4 and BA.5 Omicron subvariants as well as the original version of the virus targeted by all previous COVID vaccines and boosters. The so-called bivalent boosters are available to anyone aged 12 and older.

Jha estimated that between 13 million and 15 million Americans will have gotten the so-called bivalent booster by the end of this week.

"We think that's a really good start. Also, let me be very clear, we need to continue and up that pace as we get into October," Jha said.

Around 11.5 million people received the updated shots over the first five weeks of the rollout, including around 3.9 million who received them over the past week, according to U.S. Centers for Disease Control and Prevention (CDC) data released on Thursday.

That represents only 5.3% of the 216 million people aged 12 or older who may be eligible to receive the shots after completing their primary vaccination series.

This year's booster campaign has not kept pace with 2021, when the United States initially authorized COVID boosters just for older and immunocompromised people. Nearly 17 million people received their third shot in the first five weeks of that vaccination campaign, according to CDC data.

President Joe Biden's administration hopes to drive up U.S. booster usage by working with medical societies nationwide and targeting areas with low vaccine confidence through a media campaign, Jha said.

He was speaking during a U.S. Department of Health and Human Services (HHS) call announcing the findings of a new study on the impact of that 2021 vaccination campaign, which found it led to around 300,000 fewer deaths and 650,000 fewer hospitalizations among people enrolled in the government Medicare health plan for those age 65 or older and the disabled.

The study was conducted by researchers in the Office of the Assistant Secretary for Planning and Evaluation at HHS.

Europe's uptake of updated booster shots has also lagged last year's pace.

Weekly vaccine doses administered in the EU were between 1 million and 1.4 million in September, compared to 6 million to 10 million a week during the year-earlier period, European Centre for Disease Prevention and Control data showed.