Vaccine drive gains speed, but COVID-19 variants raise worries. Here’s the latest virus news.

The drive to vaccinate Americans against the coronavirus is gaining speed and newly recorded cases have fallen to their lowest level in three months, but authorities worry that raucous Super Bowl celebrations could fuel new outbreaks.

More than 4 million more vaccinations were reported over the weekend, a significantly faster clip than in previous days, according to the Centers for Disease Control and Prevention.

Nearly one in 10 Americans have now received at least one shot. But just 2.9% of the U.S. population has been fully vaccinated, a long way from the 70% or more that experts say must be inoculated to conquer the outbreak.

Evidence is mounting that having COVID-19 may not protect against getting infected again with some of the new variants. People also can get second infections with earlier versions of the coronavirus if they mounted a weak defense the first time, new research suggests.

How long immunity lasts from natural infection is one of the big questions in the pandemic. Scientists still think reinfections are fairly rare and usually less serious than initial ones, but recent developments around the world have raised concerns.

In other developments:

• After seeing two academic years thrown off course by the pandemic, school leaders around the country are planning for the possibility of more distance learning next fall at the start of yet another school year.
• California joined with the federal government to open two new mass vaccination centers as test areas for new President Joe Biden’s effort to create 100 such sites nationwide in 100 days.
• Transportation Secretary Pete Buttigieg will quarantine for 14 days after a member of his security detail tested positive for COVID-19. Buttigieg tested negative Monday and has not shown any symptoms.
• Republican Rep. Ron Wright of Texas, who had lung cancer and was hospitalized after testing positive for COVID-19 last month, has died, his office said Monday. He was 67.
• Iowa’s Republican governor lifted mask and social distancing mandates without conferring first with public health officials in her own administration, according to lawmakers who spoke Monday with public health officials.
• South Africa seeks a new virus vaccination plan after deciding not to use AstraZeneca jab, fearing it’s not effective enough against the country’s dominant variant.
• Delta Air Lines said Monday it will continue to block some seats on all flights through spring break and Easter to provide a bit more space between passengers.

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