The U.S. has launched a campaign to offer boosters of Pfizer's COVID-19 vaccine to millions of Americans even as federal health officials stressed the real problem remains getting first shots to the unvaccinated.

The inequity of COVID-19 vaccine distribution will come into sharper focus Thursday as many of the African countries whose populations have little to no access to the life-saving shots step to the podium to speak at the U.N.'s annual meeting of world leaders.

Already, the struggle to contain the coronavirus pandemic has featured prominently in leaders' speeches — many of them delivered remotely exactly because of the virus. Country after country acknowledged the wide disparity in accessing the vaccine, painting a picture so bleak that a solution has at times seemed impossibly out of reach.

Racism, the climate crisis and the world's worsening divisions will take center stage at the United Nations on Wednesday, a day after the U.N. chief issued a grim warning that "we are on the edge of an abyss."

For the first time since the COVID-19 pandemic began, more than two dozen world leaders appeared in person at the U.N. General Assembly on the opening day of their annual high-level meeting. The atmosphere was somber, angry and dire.

Coronavirus cases are surging to the worst levels of the pandemic in a rebel stronghold in Syria — a particularly devastating development in a region where scores of hospitals have been bombed and that doctors and nurses have fled in droves during a decade of war.

The total number of cases seen in Idlib province — an overcrowded enclave with a population of 4 million, many of them internally displaced — has more than doubled since the beginning of August to more than 61,000. In recent weeks, daily new infections have repeatedly shot past 1,500, and authorities reported 34 deaths on Sunday alone — figures that are still believed to be undercounts because many infected people don't report to authorities.

COVID-19 has now killed about as many Americans as the 1918-19 Spanish flu pandemic did — approximately 675,000.

The U.S. population a century ago was just one-third of what it is today, meaning the flu cut a much bigger, more lethal swath through the country. But the COVID-19 crisis is by any measure a colossal tragedy in its own right, especially given the incredible advances in scientific knowledge since then and the failure to take maximum advantage of the vaccines available this time.

Johnson & Johnson released data showing that a booster dose to its one-shot coronavirus vaccine provides a strong immune response months after people receive a first dose.

J&J said in a statement Tuesday that it ran two early studies in people previously given its vaccine and found that a second dose produced an increased antibody response in adults from age 18 to 55. The study's results haven't yet been peer-reviewed.

The Beizhong International Travel Agency in the eastern city of Tianjin has had only one customer since coronavirus outbreaks that began in July prompted Chinese leaders to renew city lockdowns and travel controls.

Most of China is virus-free, but the abrupt, severe response to outbreaks has left would-be tourists jittery about traveling to places they might be barred from leaving. That has hit consumer spending, hindering efforts to keep the economic recovery on track.

World Health Organization chief Tedros Adhanom Ghebreyesus and WHO Regional Director for the Eastern Mediterranean Ahmed Al Mandhari have issued a joint statement on their visit to Lebanon this week.

“We have just concluded a two-day visit to Beirut, Lebanon to reiterate our commitment to the people of Lebanon and express our solidarity and continued support,” the statement said.

Just one month ago, President Joe Biden and his health advisers announced big plans to soon deliver a booster shot of the coronavirus vaccine to all Americans. But after campaigning for the White House on a pledge to "follow the science," Biden found himself uncharacteristically ahead of it with that lofty pronouncement.

Some of the nation's top medical advisers on Friday delivered a stinging rebuke of the idea, in essence telling the White House: not so fast.

The World Health Organization's director general has expressed deep concern about the impact of Lebanon's economic meltdown and multiple crises on the wellbeing of the nation, and said the brain drain among the country's health workers is particularly worrisome.

Tedros Adhanom Ghebreyesus spoke following meetings with senior Lebanese officials and visits to health facilities and practitioners over the past two days. He said the country of 6 million -- including over 1 million Syrian refugees -- needs emergency and development support to tackle shortages of medicines, fuel, and structural problems such as migration of medical professionals.