Last checked at 
By Nancy Lapid
Dec 13 (Reuters) - 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.
Vaccines appear weak vs Omicron infection, better vs severe
disease
Vaccine effectiveness against symptomatic infection from the
Omicron variant of the coronavirus is likely to be much lower
than against earlier variants, but they may still offer
substantial protection against severe disease, a new analysis
suggests.
Billy Gardner and Marm Kilpatrick from the University of
California, Santa Cruz developed computer models incorporating
data on COVID-19 vaccines' efficacy against earlier variants and
initial data on the Pfizer/BioNTech vaccine
against Omicron. Their models suggest that early after two doses
of an mRNA vaccine from Pfizer/BioNTech or Moderna,
efficacy against symptomatic infection from Omicron is only
about 30%, down from about 87% versus Delta, they reported on
Sunday on medRxiv https://www.medrxiv.org/content/10.1101/2021.12.10.21267594v2
ahead of peer review. Protection against symptomatic infection
is "essentially eliminated" for individuals vaccinated more than
four months earlier. Boosters restore protection to about 48%,
"which is similar to the protection of individuals with waned
immunity against the Delta variant (43%)," Kilpatrick said.
"Importantly, protection against severe disease is much
higher" for all categories: recently vaccinated, waned, or
boosted. "We estimated that protection against severe disease
was 86% for recent mRNA vaccination against Omicron, 67% for
waned immunity, and 91% following 3rd dose boosters," Kilpatrick
said. "There are still no direct estimates of vaccine
effectiveness for severe disease from any country yet, so our
estimates cannot be compared to direct estimates yet."
COVID-19 vaccines may reduce long COVID burden
COVID-19 vaccines may contribute to a reduction in the
health burden of long COVID, new findings suggest.
Researchers analyzed survey responses from 28,356 adults
ages 18 to 69 from across the UK who had previously had
COVID-19, nearly one-quarter of whom had reported troublesome
lingering symptoms. The likelihood that participants would
report long COVID symptoms at least 12 weeks after infection
fell by 13% after the first vaccine dose, the researchers
reported on Thursday on medRxiv https://www.medrxiv.org/content/10.1101/2021.12.09.21267516v1
ahead of peer review. It was unclear whether this improvement
continued between the first and second doses. A further 9%
reduction in the odds of persistent symptoms after the second
vaccine dose "did appear to be sustained, at least over the
follow-up period of 67 days on average," said study leader
Daniel Ayoubkani of the UK Office for National Statistics. The
same was true for long COVID symptoms severe enough to hamper
daily activities, and the pattern was similar regardless of
whether participants received vaccines from AstraZeneca,
Pfizer/BioNTech, or Moderna.
"However," Ayoubkani noted, "we can't say from this study
if, or how, vaccination caused the observed changes in symptoms,
and more follow-up time is needed to assess whether the
improvement will be sustained in the longer term and the impact
of booster doses and new variants."
Good antibody levels from vaccines no guarantee of other
immune defenses for some
In some patients on immunosuppressive drugs, COVID-19
vaccines may induce protective antibodies without inducing good
second-line immune defenses, leaving them at risk for severe
illness if they do become infected, researchers say.
Vaccines reduce the severity of illness by inducing T cells
in the immune system to recognize and eliminate virus-infected
cells. In 303 patients on immune-suppressing therapies for
inflammatory bowel disease, researchers used a new molecular
measurement tool to count the numbers of antiviral T cells
induced by COVID vaccines. "Overall, a substantial number of
vaccinated patients - about 20% - had minimal antiviral T cell
levels, even though most had high antiviral antibodies," said
study leader Jonathan Braun of Cedars-Sinai Medical Center in
Los Angeles.
Age, sex and specific immunotherapies might be associated
with patients' T-cell response to the vaccines, but the bottom
line is that antibody levels after vaccination do not
necessarily predict T cell responses, his team said in a report
posted on Wednesday on medRxiv https://www.medrxiv.org/content/10.1101/2021.12.08.21267444v1
ahead of peer review. Levels of antiviral T cells are not often
measured, Braun said, leaving open important questions. Among
them: How frequent are vaccinated individuals with low antiviral
T cell levels in the general population? and, Do boosters help
such individuals elevate their antiviral T cell levels?
Click for a Reuters graphic https://tmsnrt.rs/3c7R3Bl on
vaccines in development.
(Reporting by Nancy Lapid; Editing by Bill Berkrot)
