Vaccination after COVID improves immunity; ivermectin fails in major trial

The following is a summary of some recent studies on covid-19. They include research that justifies further studies to confirm the results and that has not yet been certified by peer review.

Vaccination after covid-19 improves immunity

Although people recovering from covid-19 usually get some immune system against re-infection, they get additional protection against vaccines, especially against serious illness, according to two studies published on Thursday in The Lancet Infectious Diseases.

A study of 22,566 people in Brazil who had recovered from covid found that all four vaccines used there – from Sinovac Biotech, AstraZeneca, Johnson & Johnson and Pfizer / BioNTech – provided significant extra protection. The effectiveness against infection starting 14 days after the end of vaccination varied from 39.4 percent for Sinovac’s CoronaVac to 64.8 percent for the Pfizer / BioNTech syringes. Efficacy against hospitalization or death ranged from 81.3 percent for CoronaVac to 89.7 percent for the Pfizer / BioNTech vaccine.

The second study, which uses data from more than 5 million people in Sweden, found that “hybrid immunity” from a combination of previous infection and receipt of either one or two doses of a vaccine provided additional protection for at least nine months. “One-dose hybrid immunity was associated with an additional 94 percent lower risk of covid-19 hospitalization, and two-dose hybrid immunity with an additional 90 percent lower risk of covid-19 hospitalization,” compared with natural immunity alone, the researchers said. None of the studies included patients infected or re-infected with the Omicron variant.

Ivermectin fails, convalescent plasma succeeds

Two gold standard studies published in The New England Journal of Medicine on Wednesday help solve questions about two controversial therapies highlighted by many early in the pandemic with decidedly mixed results – failure of the antiparasitic drug ivermectin and success of antibody-rich blood plasma from COVID -19 survivors.

In Brazil, 3,515 patients with covid-19 symptoms for a week or less and at least one serious risk factor were randomly assigned to receive ivermectin once daily for three days, one additional treatment or placebo. Four weeks later, ivermectin could not lead to a lower frequency of hospital stays or prolonged emergency visits, the researchers reported The horseworming agent was popular with conservative commentators and anti-vaccine people despite warnings from health authorities not to use it to treat covid.

For the study of so-called convalescent plasma, US researchers registered more than 1,000 mostly unvaccinated adults within eight days of the onset of covid-19 symptoms. Half of the participants were randomly assigned to receive a convalescent plasma transfusion. Four weeks later, 2.9 percent of those who received the plasma had been hospitalized for covid-19, compared with 6.3 percent of those who did not. After taking into account individuals’ risk factors, the treatment reduced the risk of hospitalization by 54 percent, the researchers said “COVID-19 convalescent plasma is available in low-income and middle-income countries, has no patent restrictions and is relatively inexpensive to produce … (and probably) less vulnerable to the onset of antibody resistance,” they added.

Omicron infects more young children, but less harmful

Among children under 5 years of age who were not eligible for the coronavirus vaccine, the Omicron variant caused 6 to 8 times more infections than the Delta variant, but severe covid-19 was less common with Omicron, US researchers found.

They reviewed data collected in 2021 and early 2022 on 651,640 children under the age of 5, including 66,692 with Delta infections and 22,772 with Omicron infections. When Delta was dominant, two to three children out of every 2,000 became infected every day, the researchers estimated. When Omicron first began circulating, that frequency rose to about five to 13 new infections per day among every 2,000 children, researchers reported on Friday in JAMA Pediatrics In mid-January 2022, more than 16 out of every 2,000 young children became infected with Omicron every day, with the highest infection rate in children under 2 years of age.

However, children infected with Omicron had a significantly lower risk of serious illness compared with similar children infected with Delta. The findings may facilitate considerations about schooling, worm use and vaccine implementation for young children, the research group said.

Click for a Reuters graphic about vaccines under development.

(Reporting by Nancy Lapid; Editing by Bill Berkrot)

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