Massachusetts is seeing an increase in COVID-19 cases among people under 30, Governor Charlie Baker said Thursday, a rise that epidemiologists said was predictable as warm weather and the lifting of restrictions drive more people out of their homes.
Meanwhile, the state vaccination campaign continues to prioritize older residents. Baker said that while hospitalizations have declined over the past few months as the state vaccinated its “most-vulnerable residents, particularly people over the age of 75,” the state is now seeing more positive cases for a younger age demographic.
“While these residents are far less likely to be hospitalized, it remains critically important for all residents, and especially young people, to continue to practice prevention strategies and not let down their guard,” he added.
According to data the state released Wednesday that included two weeks of numbers from March 7 to March 20, residents age 19 and younger constituted the highest number of positive cases, with 5,807, and those between 20 and 29 had the second-highest number of infections, with 4,822.
But younger people were less likely to require major medical care: Despite the thousands infected, only eight people under 20 were hospitalized during that period, and only three people age 20 to 29 were hospitalized, compared to 35 hospitalizations among the 298 people age 80 or over who were infected.
Dr. Marc Lipsitch, a professor of epidemiology at the Harvard T.H. Chan School of Public Health, said the spike among young people is likely related to the restlessness many are experiencing after a year of the pandemic and a winter spent inside — a kind of cabin fever that is probably more acute for younger people.
“Everybody is getting more active,” he said in an interview Thursday. “People are getting really tired of being cooped up.”
State education officials also reported an uptick among public school students and school staff members on Thursday, with 682 new coronavirus cases among students and 228 among staff for the week that ended Wednesday. The combined total of new cases — 910 — was the highest weekly total since mid-to-late January.
The overall rate of coronavirus cases reported in the state has been moving up slightly for about the past two weeks, from a seven-day average slightly above 1,300 to a seven-day average of 1,678 on Wednesday.
The increase worries at least one health expert, who said the state’s reopening and variants of the virus could be major factors.
“Absolutely, we should be concerned,” said Northeastern University epidemiologist Sam Scarpino.
Across age groups, test positivity rates have been edging upward, and in the past few days hospitalizations have followed suit.
Scarpino attributed the case increases both to the arrival of coronavirus variants and to people letting down their guard as Governor Charlie Baker has loosened coronavirus restrictions.
“This is exactly the reason that so many of us were saying it was too soon to be relaxing measures,” he said.
The UK variant of the virus “is widespread in Massachusetts and is circulating within communities,” the state said Thursday, and variants first discovered in Brazil and South Africa are also present in the state.
Increases have also been seen in a number of other states. Experts are worried an alarming spike in Michigan might be a sign of trouble ahead.
Meanwhile, the pace of coronavirus vaccinations in Massachusetts stopped climbing and has wavered up and down in the past two weeks.
The seven-day average of total doses administered edged over 60,000 on March 9 and March 10. The numbers have fluctuated between 50,000 and 60,000 since, rising in recent days to the high 50,000s.
Massachusetts residents 75 and older are the age cohort that has the highest number of fully vaccinated people, according to state data.
More than 1.1 million Massachusetts residents have been fully vaccinated against COVID-19, according to state data, while more than 1.9 million residents have received their first dose.
Scarpino said that while vaccinated older people may be protected, younger people can still get the disease, and there will still be hospitalizations and deaths from it. Some people will also get long COVID, afflicted with symptoms for months.
He said the state should have allowed more time for vaccinations and for warmer weather to set in that would allow more outdoor dining and gatherings and better indoor ventilation.
“We could have gotten out of this without another surge by following the public health guidelines that we know work,” he said.
At Baker’s press briefing Thursday, he encouraged Massachusetts residents to continue engaging in the recommended public health measures that help stop the spread of the virus.
“Vaccines are here and that’s a great thing, but we’re still in a race against time, especially as supply remains constrained,” Baker said. “To ensure that we can stay on track and beat back the virus, provide vaccines, and get back to normal, we continue to urge residents to do your part to stop the spread.”
Martin Finucane and Felicia Gans of the Globe staff contributed to this report.
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