A nosocomial outbreak of SARS-CoV-2 Delta variant infected 42 patients, staff and family members; 39 were fully vaccinated. The attack rate was 10.6% (16/151) among exposed staff and reached 23.7% (23/97) among exposed patients in a highly vaccinated population, 16–26 weeks after vaccination (median: 25 weeks). All cases were linked and traced to one patient. Several transmissions occurred between individuals wearing face masks. Fourteen of 23 patients became severely sick or died, raising a question about possible waning immunity.
The authors concluded:
“This communication … challenges the assumption that high universal vaccination rates will lead to herd immunity and prevent COVID-19 outbreaks … In the outbreak described here, 96.2% of the exposed population was vaccinated. Infection advanced rapidly (many cases became symptomatic within 2 days of exposure), and viral load was high.”
According to the paper, the outbreak originated from a fully vaccinated haemodialysis patient in his/her 70s who was admitted with fever and cough and placed in a room with three other patients.
The patient had not been tested for SARS-CoV-2 on admission day, because his/her symptoms were mistaken for a possible bloodstream infection exacerbating congestive heart failure.
To determine the source of the outbreak, researchers conducted phylogenetic analysis on the whole-genome SARS-CoV-2 sequences that were available for 12 cases in the outbreak, including staff and patients from Wards A, B and C and dialysis departments.
All were allegedly infected with the Delta variant and epidemiologically and phylogenetically connected to the same outbreak, except for one case. That case and three staff members were not considered part of the outbreak.
“This is a very interesting paper and it is scientifically very sound,” said Dr. Brian Hooker, Ph.D., P.E., Professor of Biology at Simpson University.
“The breakthrough rate of 96.2% of the vaccinated population shows that in this instance, the vaccine was virtually useless in preventing transmission,” Hooker said. “It should also be noted the two reported cases among unvaccinated patients were mild, whereas six of the vaccinated patients died.”
According to a new pre-print study submitted for peer review, Pfizer/BioNTech vaccine antibodies disappear within seven months.
Six months after receiving the second dose of Pfizer’s two-shot vaccine, many recipients no longer have vaccine-induced antibodies that can immediately neutralize worrisome SARS-CoV-2 variants.
Researchers analysed blood samples from 46 healthy, mostly young or middle-aged adults after receipt of the two doses and again six months after the second dose.
“Our study shows vaccination with the Pfizer-BioNtech vaccine induces high levels of neutralizing antibodies against the original vaccine strain, but these levels drop by nearly 10-fold by seven months” after the initial dose, Bali Pulendran of Stanford University and Mehul Suthar of Emory University said in an email to Reuters.
In roughly half (47%) of all subjects, neutralizing antibodies that can block infection against alleged Covid-19 variants, such as Delta, Beta and Mu, were undetectable at six months after the second dose, the study showed.
Neutralizing antibodies are not the immune system’s only defense against the virus. Still, they “are critically important in protecting against SARS-CoV-2 infection,” said Pulendran and Suthar.
Compare this infection rate with the countries not in the West and not highly vaccinated and the picture becomes crystal clear.