(CNN) — Los Angeles County, the most populous in the United States, is experiencing an “exponential growth” in COVID-19 cases as delta becomes the dominant strain, according to local health officials.
The jump reflects spikes in other parts of the country over the past week, as experts warn of high delta transmissibility.
“We continue to see an increase in cases and hospitalizations,” Los Angeles County Public Health Director Barbara Ferrer said Thursday. “Fortunately, deaths remain relatively low, but as hospitalizations continue to increase, we anticipate that deaths could also increase.”
While 60% of those 16 and older have been fully vaccinated, the county’s case rate rose from 1.74 cases to 3.5 cases per 100,000 people in one week, according to a news release from the Los Angeles County Department of Public Health.
The vast majority of those who test positive in the county are not vaccinated, accounting for 99.96% of all new infections, according to the news release.
Overall, the state’s covid-19 positivity rate – the percentage of all tests that are positive – has tripled since California fully reopened last month.
The rate is now surpassing 2% for the first time since early March, after hitting a low of 0.7% in early June, according to new data from the state Department of Public Health.
The delta variant, first detected in India, has been found in 43% of new samples sequenced in California, the state said.
And it also constitutes more than 50% of the sequenced samples nationwide. In some areas, it’s even more, according to Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention.
“Although we expected the delta variant to become the dominant strain in the United States, this rapid increase is concerning,” he said.
In parts of the Midwest and High Mountain states, CDC data suggests it accounts for about 80% of cases.
“Widespread vaccination is what will really turn us around the corner of this pandemic,” Walensky said. “Please know that if you are not vaccinated, you are still susceptible.”
Pfizer Says It Is Developing A Booster Vaccine After Seeing Waning Immunity
Meanwhile, Pfizer announced Thursday that it was seeing waning immunity from its vaccine, made in partnership with BioNTech, and was resuming its efforts to develop a booster vaccine to offer greater protection against variants.
“As seen from real-world data published by the Israel Ministry of Health, the efficacy of the vaccine in preventing infections and symptomatic diseases has decreased six months after vaccination, although the efficacy in preventing serious diseases remains high.” Pfizer said in an emailed statement to CNN.
Israel’s Health Ministry said in a statement earlier this week that it had seen the efficacy of Pfizer’s vaccine drop from more than 90% to about 64% as the delta variant spread.
But hours after Pfizer’s statement, the FDA and the Centers for Disease Control (CDC) issued a joint statement saying that Americans still don’t need booster shots.
Dr. William Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University Medical Center, supported the US government’s position.
“The answer is that our vaccines are still very, very effective in keeping us out of the hospital, in preventing serious illness. That’s what they were designed for,” he told CNN on Thursday. “Now, it’s an advantage if they can also prevent what we call infection. You can get infected, have mild symptoms, or no symptoms. They greatly decrease that possibility. But they can’t turn it off completely.”
Vaccination gap widens
While experts have long emphasized that vaccines are our best defense against the pandemic, overall rates have dropped in the United States.
Less than half of Americans are fully vaccinated as of Thursday, CDC data shows. And the difference in vaccination rates between Republicans and Democrats has increased in the past two months, a report released Thursday by the Kaiser Family Foundation shows.
Vaccination rates are rising faster in counties that voted for Joe Biden in the 2020 presidential election than in counties that voted for Donald Trump, according to the new study.
The team used data comparing CDC vaccination figures in all counties with the results of the 2020 presidential election.
In April 2021, the counties where the most people voted for Trump had an average vaccination rate of 20.6%, compared to 22.8% in the counties that elected Biden, the study found. As of July 2021, the average vaccination rate in Trump trend counties was 35% and 46.7% in Biden trend counties. The gap increased 9.5 percentage points in less than three months.
The researchers said these numbers account for the importance of targeted vaccination efforts that account for partisan opposition.
“A key component of any effort to increase vaccination rates among Republicans will be identifying the right messengers,” the researchers wrote.
“Republicans are more likely to trust their doctors and employers to provide reliable information on COVID-19 vaccines, while government sources are less reliable.”
CNN’s Jamie Gumbrecht, Maggie Fox, Virginia Langmaid, and Cheri Mossburg contributed to this report.
George is Digismak’s reported cum editor with 13 years of experience in Journalism