With time and without masks, COVID-19 vaccines wane in protection, study
finds

Date:
September 2, 2021
Source:
University of California - San Diego
Summary:
A study of highly vaccinated health workers found that the more
contagious delta variant, combined with the masking mandate end,
was associated with increased breakthrough cases, paralleling
exponential rise of COVID-19 infections in the San Diego community.



FULL STORY ==========================================================================
In a letter to The New England Journal of Medicine, publishing online
September 1, 2021, an interdisciplinary team of physicians and public
health experts at University of California San Diego measured the
effectiveness of COVID-19 mRNA vaccines among health workers at UC
San Diego Health, most notably during the emergence of the highly
transmissible delta virus variant and coincident with the end of the
state's mask mandate, allowing fully vaccinated persons to forgo face
coverings in most places.


==========================================================================
The letter's authors report that the effectiveness of both the Pfizer
and Moderna mRNA COVID-19 vaccines significantly waned over time. Both
vaccines were granted emergency use authorization by the Food and Drug Administration in December 2020, with vaccinations of the UC San Diego
Health work force beginning the same month for health care workers with
direct, patient-facing duties.

In the letter, the authors note that from March through June 2021 vaccine effectiveness against symptomatic infection was estimated to exceed 90
percent; by July, however, it had fallen to approximately 65 percent.

"The decline in effectiveness is not entirely surprising," said co-senior author Francesca Torriani, MD, professor of clinical medicine in the
Division of Infectious Diseases and Global Public Health in the UC San
Diego School of Medicine and program director of Infection Prevention
and Clinical Epidemiology at UC San Diego Health.

"Clinical trial data suggested decreased effectiveness would occur several months after full vaccination, but our findings indicate that confronted
by the delta variant, vaccine effectiveness for mildly symptomatic disease
was considerably lower and waned six to eight months after completing vaccination." UC San Diego Health, with a work force of approximately
19,000, operates a robust SARS-CoV-2 testing program. If an employee
reports even one mild symptom of COVID-19 during daily screening or an identified exposure, a test is triggered.



==========================================================================
Then and now, UC San Diego Health has maintained rigorous, mandatory
masking and transmission mitigation measures throughout its hospitals
and clinical facilities. Diagnosed positive cases among health workers
have universally been identified as community acquired.

In December 2020, workers at UC San Diego Health, like the population
overall, began experiencing a surge of SARS-CoV-2 infections, the virus
that causes COVID-19.

The situation improved significantly after UC San Diego Health began
to inoculate employees using the Pfizer and Moderna vaccines. By March
2021, 76 percent of workers were fully vaccinated, rising to 83 percent
by July 2021.

Concomitant with increased vaccination coverage was a decline between
March and June in the number of workers reporting at least one symptom
of COVID-19 and a positive PCR test. That number declined to fewer than
30 employees per month.

In July 2021, however, cases among this highly vaccinated population
began to rise again, coincident with the emerging dominance of the delta variant in San Diego and the ending of California's masking mandate on
June 15. By July, 125 workers had been diagnosed with SARS-CoV-2 and
unlike in previous months when approximately 20 percent of these cases
involved vaccinated workers, the percentage had risen to 75 percent.



========================================================================== Notably, the vaccines still provide significant protection from severe infection outcomes, such as hospitalization and death. Among the UC San
Diego Health employee cases documented, no hospitalizations were reported
in vaccinated individuals and only one among unvaccinated persons.

"Unlike what was experienced with other variants, with the delta variant parents are frequently getting infected by their young children, ages 5
to 11," said co-first author Lucy Horton, MD, MPH, an assistant professor
of medicine in the Division of Infectious Diseases and director of the
UC San Diego Health COVID-19 case investigation and contact tracing
team. "Unvaccinated people are seven times more likely to test positive
for COVID-19 than those who are fully vaccinated. More importantly,
while children rarely need medical attention, unvaccinated adults are 32
times more likely to require hospitalization compared to those who are
fully vaccinated." Vaccine effectiveness was linked to the passage of
time. For workers diagnosed in July, those who became fully vaccinated
in January and February had higher infection rates than those vaccinated
later in March through May. The infection rate among unvaccinated persons
has remained consistently higher than for any vaccinated group, although
the difference in rates between the two groups has decreased over time.

"The dramatic change in vaccine effectiveness from June to July
is likely due to a combination of factors," said co-author Nancy
Binkin, MD, MPH, professor of epidemiology in the UC San Diego School
of Medicine and Herbert Wertheim School of Public Health and Human
Longevity Science. "It's the emergence of the delta variant and waning
immunity over time, compounded by the end of broad masking requirements
and the resulting greater exposure risk throughout the community."
Co-senior author Shira Abeles, MD, an assistant professor of medicine
in the Division of Infectious Diseases who has led the COVID-19
vaccination effort at UC San Diego Health, said the findings underscore
the importance of rapidly reinstating key interventions, such as indoor
masking and intensive testing strategies, plus continuing efforts to
boost vaccination rates.

"Similar findings are being reported in other settings in the U.S. and internationally, and it is likely that booster doses will be necessary." Co-authors include: Jocelyn Keehner (co-first author), Louise C. Laurent,
David Pride and Christopher A. Longhurst, all at UC San Diego.

========================================================================== Story Source: Materials provided by
University_of_California_-_San_Diego. Original written by Scott
LaFee. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jocelyn Keehner, Lucy E. Horton, Nancy J. Binkin, Louise C. Laurent,
David Pride, Christopher A. Longhurst, Shira R. Abeles, Francesca J.

Torriani. Resurgence of SARS-CoV-2 Infection in a Highly Vaccinated
Health System Workforce. New England Journal of Medicine, 2021;
DOI: 10.1056/NEJMc2112981 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210902101114.htm

--- up 8 hours, 25 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)