Some four in 10 COVID-19 patients in a hospital in California during late December 2021 and most of January were fully vaccinated, according to a new study.
The percentage of fully vaccinated patients in an academic hospital in California climbed from 25 percent in the summer of 2021 to 40 percent after the Omicron virus variant became dominant in the United States, researchers said in the study, published by the Centers for Disease Control and Prevention’s (CDC) quasi-journal.
The number of unvaccinated patients in the hospital, which was not identified dropped from 71 percent when the Delta virus variant was dominant to 56 percent following Omicron’s emergence, according to the study, which analyzed electronic health records.
Fully vaccinated refers to patients who received two doses of the Moderna or Pfizer-BioNTech COVID-19 vaccines, or those who got the single-shot Johnson & Johnson jab, at least 14 days before getting a positive COVID-19 test associated with their hospitalization. Unvaccinated in the study was counted as patients with no documentation of receipt of any COVID-19 vaccine before they received a positive test.
The remaining hospitalized patients had received one dose of a vaccine or had received two doses, but 14 days had not elapsed following their second shot.
About 10 percent of the patients were fully vaccinated and had gotten a booster shot.
“Compared with the period of Delta predominance, a higher proportion of adults hospitalized during Omicron predominance were fully vaccinated,” researchers wrote in the study, which was reviewed by CDC officials before publication.
“Increases in infections among vaccinated persons during the period of Omicron predominance were likely driven both by waning vaccine-derived immunity over time and by relative resistance to vaccine neutralization in the Omicron variant compared with the Delta variant,” added Dr. Peter Chen, director of the Division of Pulmonary and Critical Care Medicine at the Cedars-Sinai Medical Center, and his co-authors.
The primary series of the COVID-19 vaccines have proven increasingly ineffective against the CCP (Chinese Communist Party) virus, which causes COVID-19, particularly after Omicron became dominant in the country.
Health officials recommend all eligible vaccinated persons get a booster to restore some of the lost protection, though it’s unclear how long the booster effects will last.
Another recent study performed by researchers in California and published by the CDC found that the COVID-19 infection and hospitalization gap between the unvaccinated and vaccinated narrowed, though vaccinated people were still less likely to get infected or be hospitalized.
Chen and the other researchers in the new paper said the data indicated patients hospitalized with the illness during Omicron predominance had less severe illness when compared to patients hospitalized during the period when Delta was dominant, but attributed the effect to the increase in numbers of adults who became fully vaccinated.
They also said that about 20 percent of the hospitalizations during the period studied post-Omicron emergence were admissions not linked to COVID-19 conditions.
Patients with a history of prior COVID-19 infection were not separated out and Chen didn’t respond to emailed questions, including why the study didn’t explore how natural immunity is holding up against Omicron.