Dr. Anthony Fauci speaks about the Omicron variant of the coronavirus during a press briefing at the White House in Washington, December 1, 2021.
Kevin Lamarque | Reuters
Omicron’s most contagious subvariant, BA.2, has more than doubled in prevalence in the past two weeks in the US and now accounts for more than 34% of Covid-19 infections that have undergone genetic sequencing , according to data released by the Centers for Disease Control and Prevention this week.
BA.2 has been steadily growing as a proportion of Covid variants circulating in the United States since February 5, when it accounted for about 1% of genetically sequenced virus samples, according to the CDC. BA.2 likely already accounts for 50% of new infections in the United States because many people take home tests that aren’t captured in official data, according to Ali Mokdad, an epidemiologist at the Institute for Health Metrics and Evaluation at the United States. University of Washington.
Data from Walgreens, which tests its pharmacies nationwide, shows BA.2 is the dominant variant at 51% of all positive Covid cases for the week ending March 19.
Although BA.2 is rising in the United States, top public health officials do not expect a dramatic further increase in new cases, largely due to the level of immunity the population enjoys from the vaccination and the ferocious epidemic during the winter wave of omicron.
“Ultimately, we’re likely to see an increase in the number of cases, as we’ve seen in European countries, especially the UK,” said White House chief medical adviser Dr Anthony. Fauci, at ABC’s “This Week.” “Hopefully we don’t see a push – I don’t think we will.”
In the UK, the number of people testing positive for Covid has jumped 16% in the past week, government data shows. Patients admitted to hospitals with the virus are also up by around 20%. BA.2 now accounts for around 44% of all positive cases in London as of March 10, according to the UK Health Security Agency.
Shoppers walk along Oxford Street in London on December 21, 2021.
Tolga Akmen | AFP | Getty Images
However, Mokdad said the situation in the United States was different from that in European countries, as there were many more omicron infections here during the winter. European nations have also drastically changed their behavior in recent weeks by lifting restrictive public health measures, which led to the outbreak. In many parts of the United States, on the other hand, restrictive measures have not been implemented during omicron, so there is not such a dramatic change in behavior to cause new infections, Mokdad said.
In the United States, new infections are down 96% from the pandemic record of more than 800,000 on January 15, according to a CNBC analysis of data from Johns Hopkins University. However, the speed of the decline has slowed and new cases appear to have almost plateaued at a seven-day average of around 31,000 new infections per day. Hospital admissions of Covid patients have fallen 90% from the peak of the omicron wave in January, according to the CDC.
Members of the Ohio National Guard help administer coronavirus disease (COVID-19) tests in Columbus, Ohio, January 5, 2022.
Gaelen Morse | Reuters
Although Mokdad expects BA.2 to account for more than 80% of new cases in the coming months, he said the variant’s doubling time has actually slowed recently. IHME predicts that cases will continue to decline in the spring and summer, with another surge possible this winter when immunity began to decline significantly.
“The pandemic phase of the virus is over in our view,” Mokdad said. “We are entering an endemic phase.”
Public health officials in England have found that the subvariant grows 80% faster than the previous version of omicron, BA.1, according to a briefing paper released earlier this month. Maria Van Kerkhove of the World Health Organization described BA.2 as the most transmissible Covid variant to date and said it was sweeping the world. The subvariant now accounts for more than 80% of sequenced Covid samples worldwide, according to an international database.
Between vaccination and infection, an estimated 95% of the U.S. population ages 16 and older had developed antibodies to the virus by the end of December 2021 before the omicron wave peaked, according to a CDC survey of samples from blood donors. Mokdad said that level of immunity puts the United States in a good position until winter, when protection begins to wear off.
Tatiana Perez, 11, receives a dose of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at a vaccination center in San Jose, Costa Rica, January 11, 2022.
Mayela Lopez | Reuters
Vaccine-induced antibodies wane after about three months, which can lead to breakthrough infections, although the shots still protect against serious disease. Healthy young people who have recovered from Covid are immune for at least 6 months, according to peer-reviewed studies in Denmark, the UK and the US. Although these studies were published before omicron, scientists in Qatar recently found that infection 10 months earlier provided about 46% protection against BA.2 disease in unvaccinated people. However, the elderly and people with weakened immune systems are much more vulnerable to reinfection.
BA.2 does not make people sicker than BA.1, which was less severe than the delta variant, according to a large real-world study by South Africa’s National Institute of Communicable Diseases. Reinfection with BA.2 – while possible – appears to be rare, according to a February study from Denmark’s Statens Serum Institut in Copenhagen. Public health authorities in the UK have come to the same conclusions about hospitalization and reinfection. Neither study has yet been peer reviewed.
“The fact that there are similar clinical manifestations of BA.1 compared to BA.2 gives me some hope that it won’t completely change the game on us the way omicron changed the game of delta,” said Jennifer Nuzzo, an epidemiologist at Johns Hopkins University.
A son and daughter hug their father, a coronavirus disease (COVID-19) patient in the intensive care unit (ICU), before his intubation procedure at Providence Mission Hospital in Mission Viejo, California, USA United, January 25, 2022.
Shannon Stapleton | Reuters
There is also no significant difference in the duration of protection Pfizer and Moderna injections offer against mild disease of BA.2 compared to BA.1, according to a study published this month by scientists. based in Qatar, which is also not peer-reviewed. The vaccines are 50% effective in preventing mild illness caused by both omicron variants three months after the second dose, but protection is negligible after this time. However, two-dose vaccines still offer more than 70% protection against hospitalization and death, and booster doses increase this protection to more than 90%.
Fauci said this week there was no need to reapply Covid restrictions at this time. The CDC said earlier this month that 98% of people in the United States live in areas where they no longer need to wear masks in public places indoors under its new Covid leadership. Public health authorities in the United States have focused on hospitalizations, rather than new infections, when assessing the threat the virus poses to communities.
A shopper wears a protective face mask as he enters a store as New York State’s new indoor masking mandates went into effect amid the spread of the coronavirus disease (COVID-19) in New York City , New York, USA, December 13, 2021.
Mike Segar | Reuters
The Biden administration is relying on a strategy of vaccination, testing, and treatment with antiviral pills to keep the virus from disrupting daily life. About 75% of adults in the United States are fully vaccinated, according to CDC data.
Dr. Paul Offit, an infectious disease expert at Children’s Hospital of Philadelphia, said the public should focus on hospitalizations, a measure of more serious illness, rather than new infections. Offit said that between vaccination and infection with omicron, there is likely enough immunity in the population to protect against a major spike in BA.2 hospitalizations.
“Right now, I’m choosing to be optimistic that we’re just going to see a lot of mild illness and not see a dramatic increase in hospitalizations,” Offit said.