The following is a summary of some recent studies on COVID-19. They include research that warrants further study to corroborate the findings and that has yet to be certified by peer review.
Fourth vaccine dose protects vs Omicron for at least a month
A fourth dose of the COVID-19 vaccine from Pfizer and BioNTech provided significant added protection against severe disease, hospitalization and death for at least a month in older individuals, according to a study conducted when the Omicron variant was dominant.
The estimated effectiveness of the fourth dose during days 7 to 30 after it was administered compared with a third dose given at least fourth months earlier was 45% against infection, 55% for symptomatic disease, 68% for hospitalization, 62% for severe disease and 74% for death, the research team reported on Wednesday in The New England Journal of Medicine.
The study compared 182,122 individuals aged 60 and older who received a fourth dose and 182,122 very similar people who had received a third dose but not a fourth.
“The results of our real-world study suggest that a fourth vaccine dose is, at least initially, effective against the Omicron variant,” the researchers said. “Additional follow-up will allow further assessment of the protection provided by the fourth dose over time.”
A recently published study that looked only at rates of breakthrough infections and serious illness after the fourth dose found that efficacy waned quickly versus infection but held steady versus severe illness.
COVID-19 may increase risk for rare eye clots. Patients with COVID-19 may have an increased risk of rare vision-threatening blood clots in the eye for months afterward, new findings suggest.
Because SARS-CoV-2 infections increase the risk of blood vessel obstructions at other sites in the body, researchers studied nearly half a million COVID-19 patients to see whether they would develop clots in the veins or arteries of the retina, the nerve tissue at the back of the eye that receives images and sends them to the brain.
Over the next six months, 65 patients had a retinal vein occlusion. While that number is low, it reflects a statistically significant 54% increase compared with pre-COVID infection rates, according to a report published on Thursday in JAMA Ophthalmology.
Retinal artery clots were 35% more common after COVID-19 than before, but that difference might have been due to chance. The clots most often occurred in patients with other conditions that increased their risk of blood vessel problems, such as diabetes, high blood pressure, and high cholesterol.
By: Nancy Lapid
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Critics:
Compared with a third vaccine dose, a fourth dose of the Pfizer/BioNTech COVID-19 vaccine lowered the risk of infection, symptomatic infection, hospitalization, severe illness, and death 52% to 76%—depending on the measure—amid the Omicron surge among older adults.
Protection against infection waned, however, after 5 weeks, but not protection against severe COVID-19. The findings were published yesterday in the New England Journal of Medicine.
Seven to 30 days after the fourth COVID-19 dose, vaccine effectiveness (VE) relative to the third dose was estimated at 45% against infection (95% confidence interval [CI], 44% to 47%), 55% against symptomatic illness (95% CI, 53% to 58%), 68% against COVID-19 hospitalization (95% CI, 59% to 74%), 62% against severe disease (95% CI, 50% to 74%), and 74% against death (95% CI, 50% to 90%).
Fourteen to 30 days after the fourth dose, VE was 52% (95% CI, 49% to 54%) against infection, 61% (95% CI, 58% to 64%) against symptomatic illness, 72% (95% CI, 63% to 79%) against hospitalization, 64% (95% CI, 48% to 77%) against severe disease, and 76% (95% CI, 48% to 91%) against death.
In the fourth week after the fourth dose, the adjusted infection rate was lower by a factor of 2.0 (95% CI, 1.9 to 2.1) than that in the three-dose group and lower by a factor of 1.8 (95% CI, 1.7 to 1.9) than that among controls.
The difference in absolute risk for COVID-19 hospitalization 7 to 30 days after a fourth vaccine dose, relative to a third, was 180.1 per 100,000 people (95% CI, 142.8 to 211.9), while it was 68.8 cases per 100,000 (95% CI, 48.5 to 91.9) for severe disease. A sensitivity analyses of VE against infection had similar results as those in the primary analysis.
Starting in the fifth week after the fourth dose, the rate ratio (RR) for infection began to fall. The adjusted rate of infection in the eighth week after the fourth dose was comparable to that of internal controls. The RR for the three-dose group relative to the four-dose group was 1.1, while the rate ratio for the internal control group, compared with the four-dose groups, was 1.0.
The RRs comparing controls with fourth-dose recipients were larger and lasted longer for severe disease. In the fourth week after the fourth dose, the adjusted rate of severe disease was lower by a factor of 3.5 than in three-dose recipients and a factor of 2.3 than in internal controls.
The adjusted rate of severe illness in the fourth week after the fourth dose was 1.6 cases per 100,000 person-days, compared with 5.5 cases per 100,000 in three-dose recipients and 3.6 cases per 100,000 in internal controls. The adjusted rate differences were 3.9 fewer cases per 100,000 person-days and 2.1 fewer cases per 100,000 than the three-dose group and internal controls, respectively.
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