President Joe Biden has been vaccinated and boosted. Here's why he still got COVID-19

An increasing number of people, including President Joe Biden, are getting infected with COVID-19 in spite of being vaccinated and boosted.

But that doesn't mean the COVID-19 vaccine isn't working.

Subvariants of the omicron variant of the COVID-19 virus, including the dominant BA.5 subvariant, are both contagious and particularly good at evading immunity, whether it's from the vaccine or a prior infection.

Yet the vaccine is still the best protection against serious illness, even if it doesn't protect against infection, federal, state and county public health officials say.

"The (COVID-19) vaccine is remarkable at keeping people out of the hospital even though the variants going around right now are very different than the original strain the vaccine was created for," said Dr. Bob England, interim director of the Arizona Partnership for Immunization and former longtime Maricopa County Health Department director.

"Joe Biden is old. I don't know what other chronic conditions he may have, but he's old, and he's at high risk of having serious COVID disease. But he is at way less at that risk because of the vaccines he got. ... Your odds are way better with the vaccine than not."

Biden, following recommendations for people ages 50 and older, is fully vaccinated and has received two boosters. Still, the White House announced Thursday that he had tested positive for COVID-19. So far, he is experiencing mild illness and is getting treated with the antiviral Paxlovid.

"Because the president is fully vaccinated, double-boosted, his risk of serious illness is dramatically lower," White House COVID-19 coordinator Dr. Ashish Jha said during a news briefing Thursday.

Here are five things to know about COVID-19 infection and the effectiveness of vaccines and boosters:

Illness is likely to be milder for those with vaccine protection.

Vaccines and booster doses "have been doing a very good job of preventing a substantial rise in hospitalizations and deaths," Don Herrington, interim director of the Arizona Department of Health Services, wrote Thursday in a blog post.

"In May, adults who were vaccinated and boosted were eight times less likely to be hospitalized and 21 times less likely to die than unvaccinated individuals."

Everyone 5 and older is recommended to get a vaccine booster dose. Individuals ages 50 and older and those 12 and older with weakened immune systems are recommended to get a second booster dose.

The Centers for Disease Control and Prevention published research on July 15 that showed third and fourth COVID-19 vaccine doses offered substantial protection among adults with healthy immune systems who were eligible to receive them early in 2022, when the omicron variant of the COVID-19 virus first emerged.

The findings suggest that currently available vaccines may provide protection against serious illness caused by the currently circulating BA.5 variant, CDC officials said.

COVID-19 vaccines and booster doses can be located at azhealth.gov/FindVaccine.

COVID-19 cases in Arizona are up because of the BA.5 subvariant.

It's not known whether Biden was infected with the BA.5 subvariant, but BA.5 is dominant both in the U.S. and Arizona.

Clinicians said many BA.5 symptoms are similar to those seen in previous variants, including congestion, headaches, cough and fever, and children tend to have more gastrointestinal symptoms, USA TODAY reported this week.

On Wednesday, state health officials added 18,135 new COVID-19 cases in Arizona and 66 new known deaths over the weeklong period ending July 16. June and July have seen relatively similar weekly case additions, with this past week's slightly higher.

Case counts are still far below the winter, state data shows, but case numbers in recent months likely are not showing the full picture of infections as many more people have used at-home test kits and may not report positive results to county health departments.

The CDC's "community level" recommendations, updated on Thursday, for a second consecutive week say residents of 10 Arizona counties should be wearing well-fitting masks indoors in public, regardless of vaccination status or individual risk, including in K-12 schools and other community settings.

The guidance is updated weekly and ranks counties as low, medium and high, or green, yellow and orange. The Arizona counties designated as “high,” where masks are recommended, are Maricopa, Pinal, Apache, Coconino, Gila, La Paz, Mohave, Navajo, Yavapai and Yuma. Greenlee, Santa Cruz, Pima, Graham and Cochise are “medium.”

The metrics are based on a county’s COVID-19 hospital bed use, COVID-19 hospital admissions and case rates for the virus over the past week. Nearly 42% of counties in the U.S. as of Thursday were designated as "high."

Masks are not explicitly recommended for communities in the medium level except for certain people, including those who are immunocompromised, at high risk for severe disease, or have a household or social contact at high risk for severe disease.

The CDC also recommends "enhanced prevention measures in high-risk congregate settings" in communities designated at the medium level.

It's still possible to be vaccinated and get sick from COVID-19, but it's less likely.

As of July 13, there had been 2,057 breakthrough deaths in fully vaccinated individuals (two doses of a two-dose vaccine), according to state health officials’ preliminary data, which works out to a breakthrough death rate of about 0.04% among fully vaccinated people.

Data from May show that 25.6% of cases, 24.9% of hospitalizations and 19.2% of COVID-19 deaths were among fully vaccinated people without a booster, with much of the rest among unvaccinated people. Fully vaccinated people with a booster made up 36.4% of reported cases, 31.5% of hospitalizations and 26% of deaths in May.

The COVID-19 virus' disproportionate impact on older adults, who are also more likely to have a booster dose, could help explain why a higher percentage of people who were fully vaccinated and boosted died of COVID-19 in April than those who were fully vaccinated and not boosted. The effectiveness of boosters also appears to wane after several months. But the precise explanation for those percentages of deaths is unclear.

Looking at the proportions of deaths by vaccination status does not tell the risk, though. State health officials recommend considering the rates of death among boosted individuals versus unvaccinated individuals, which show significantly lower death rates in vaccinated and boosted individuals compared with unvaccinated individuals.

Unvaccinated people 12 and older in Arizona had a 1.8 times greater risk of testing positive for COVID-19, 8 times greater risk of hospitalization from COVID-19 and 21 times greater risk of dying from COVID-19 in May compared with fully vaccinated people with a booster, according to a state analysis.

Arizonans would be better protected as a whole if more of us were vaccinated.

Arizona's rate of fully vaccinated people out of the total population was 62.5%, which was behind the national rate of 67.1%, according to the CDC as of July 13.

A higher level of vaccinated people in a community will provide more protection for the community as a whole, particularly those who are more vulnerable. The point where a large portion of a community becomes immune to a disease is often referred to as "herd immunity."

"If more people are vaxxed and boosted, fewer people will get infected," said England, of the Arizona Partnership for Immunization. "The whole impact will be less. It's that simple."

Out of people ages 5 and older, 66.5% of those in Arizona were fully vaccinated, compared with 71.3% at the national level, CDC data shows.

Health experts strongly recommend booster shots for those eligible, especially with the omicron variant spreading. About 47.3% of fully vaccinated Arizonans over the age of 18 had received a first booster shot as of July 6, below the national rate of 51.3% for that same age group.

"COVID-19 has been especially dangerous for older people throughout the pandemic, but data on the current increase in cases provides even more reason for those in this age group to make sure their vaccines are up to date," Herrington wrote in his blog post.

"Compared to the winter surge driven by the Omicron variant, Arizona has since February seen a greater share of cases, hospitalizations, and deaths among those 65 and older."

Get a second booster shot now rather than waiting for variant-specific boosters, CDC says.

"COVID-19 vaccines remain our single most important tool to protect people against serious illness, hospitalization, and death," the CDC said July 15.

"Getting vaccinated now will not prevent you from getting an authorized variant-specific vaccine in the fall or winter when they are recommended for you."

Given recent increases in deaths and hospitalizations associated with the BA.5 variant, everyone should stay up to date with recommended COVID-19 vaccinations, including additional booster doses for those who are moderately to severely immunocompromised and adults over 50, officials with the federal agency say.

'It is spreading everywhere': What to know about latest COVID-19 wave in Arizona

Generally, public health experts and health providers say staying up to date on vaccines and boosters will provide the best protection right now, when the virus that causes COVID-19 is still spreading.

"If you haven't already had COVID, you don't want to have COVID. ... In my view, first is worst," Dr. Joe Gerald, an associate professor of public health policy at the University of Arizona's Mel and Enid Zuckerman College of Public Health, told The Arizona Republic earlier this month.

"The greatest risk from COVID occurs in that first infection, whether it's severe illness, death, long COVID. It's avoiding that first one that provides the greatest benefit to you individually."

Republic reporter Alison Steinbach contributed to this article

Reach the reporter at Stephanie.Innes@gannett.com or at 602-444-8369. Follow her on Twitter @stephanieinnes.

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This article originally appeared on Arizona Republic: Vaccinated people are getting COVID-19. But the vaccine still works