• Moderna Chief Medical Officer Paul Burton said Covid is entering an endemic phase in the Northern Hemisphere.
• Burton said cases, hospitalizations and deaths will be more stable when Covid is endemic.
• However, some people will still get sick and die from Covid when the virus is endemic, he said.
• Moderna executives said a booster shot that targets both the omicron and delta variants will be needed this year.

Senior executives at Moderna on Thursday said Covid-19 is shifting from a pandemic to an endemic phase in some parts of the world, with regions in the Northern Hemisphere hopefully entering a period of relative stability.

"We do believe that we are transitioning into an endemic phase marked by a period of stability in case counts, hospitalizations and deaths at least in the Northern Hemisphere," Moderna Chief Medical Officer Paul Burton told analysts during a call Thursday morning after the company reported fourth-quarter earnings.

North America, Europe, most of Asia and much of Africa are in the Northern Hemisphere. However, Burton said Moderna is closely monitoring the trajectory of the virus in the Southern Hemisphere, which includes large nations such as Brazil and South Africa, as winter approaches there.

Burton said Covid will continue to circulate during an endemic phase but at a more static and predictable rate. It will likely follow seasonal patterns like other respiratory viruses, such as the flu, he said. However, Burton warned people will still get sick and die from Covid even when the virus becomes endemic. He noted that other endemic coronaviruses cause 340,000 hospitalizations and 20,000 deaths annually for people older than 65 years old, citing data from the Organization for Economic Cooperation and Development.

Moderna CEO Stephane Bancel told CNBC on Thursday that although Covid is entering an endemic phase in some parts of the world, people will need another booster shot in the fall. This is particularly true for individuals over 50 and those who are at high risk due to underlying health conditions, he said.

"I got a flu shot every year, not that I was worried of dying or getting hospitalized — I just don't want to get sick," Bancel said. On Thursday's earnings call, Bancel said he expects Covid shots will have a similar role in the future as the virus becomes seasonal.

"Some countries like the U.K. and others wanted to secure supply because they believe very deeply that the endemic market will require annual boosters," Bancel said.

Moderna on Thursday announced that it is developing a booster vaccine that targets omicron and other Covid variants such as delta. Burton said the current booster protects against hospitalization from delta and to a lesser extent from omicron. However, he said the effectiveness of the vaccine declines over time.

"We do see waning of protection over time against hospitalization due to infection, and this fits with the profound immune evasion we know to be the case with omicron," Burton said. Due to waning immunity, a booster that targets both the omicron and delta variants will be needed in 2022, he said.

"This is because delta, as we know, is associated with strong pathogenicity, and omicron as we have seen due to its transmissibility and infectivity is also associated with substantial morbidity and strain on health-care systems through sheer bulk of cases," Burton said. "Protection against both delta and omicron may well be necessary in the next boost of vaccination."

Burton said the disease burden and deaths have declined from their highest levels during the first wave of infection, when no one had immunity to the virus.

"With each subsequent wave in mid-2021 with delta and late 2021 and early 2022 with omicron, the morbidity observed from these waves tended to be less severe, certainly relative to the first wave, as our immune systems became more experienced at fighting the SARS-CoV-2-virus," Burton said.

In the U.S., Covid cases have fallen 90% from their peak level during the omicron wave on Jan. 15. The U.S. is reporting a seven-day average of about 80,000 new cases per day, according to data compiled by Johns Hopkins University, roughly one-tenth of the pandemic record of more than 800,000 average daily cases.

Hospitalizations have also fallen sharply to about 60,000 patients with Covid in U.S. hospitals from a high mark of more than 159,000 on Jan. 20, based on a seven-day average of data from the Department of Health and Human Services.

Worldwide, Covid cases are down 21% and new deaths have fallen 8% over the previous week, according to data from the World Health Organization. Infections are dropping in every region except the Western Pacific. However, new infections remain high, with 12 million reported for the week ended Feb. 20. More than 67,000 people died from Covid worldwide during that week alone.