Thanks to feedback from this post I was able to find the article and read it. I did ask for anyone who could get the full article to post it. Thanks for posting the link I wanted.
It was not straight forward for me to get this article. First I did not notice the link to the abstract in the article; then my Firefox installation would not activate the link in the abstract to the full article Finally I tried the Opera browser and after asking me for permission to load cookies, it downloaded the original article.
31 pages reporting on a hospital in Vietnam where 7.7% of the staff appear to have got the delta variant from a single source. All but 2 with the virus were fully vaccinated with the AZ vaccine. The other 2 had only the first shot.
I might later summarise the article in layman's terms, but for now I post the Discussion section of the preprint article verbatim. Here in Melbourne we had a similar outbreak last year among healthcare workers in Frankston hospital but I have seen no similar report.
"We studied Oxford-AstraZeneca vaccine breakthrough infections associated with SARS-255CoV-2 Delta variant among healthcare workers of a major hospital for infectious diseases in HCMC, Vietnam between 11th and 25th June 2021 (week 7 and 8 after the second dose).
62/69 infected cases participated in the clinical study. One required cannula oxygen supplementation for three days but all made full recovery in line with recent reports regarding the vaccine effectiveness in protecting against severe disease. However, we found strong evidence demonstrating for the first time that fully vaccinated healthcare workers could still pass the virus between each other.
Indeed, the 23 whole-genome sequences of SARS-CoV-2 obtained from the infected cases263clustered tightly on the phylogenetic tree, but separately from the contemporary Delta264variant genomes obtained from cases of community transmission in HCMC. This strongly suggested that these individuals likely caught the virus from a single introduction into the hospital. Additionally, because only 1 out of the first 53 infected cases of the outbreak were symptomatic at diagnosis, presymptomatic and/or asymptomatic transmission had occurred between the vaccinated members of staff of HTD. This was likely attributed to several factors. Firstly, high viral loads, >7 log10 copies per mL, which was strongly correlated with positive culture (i.e. infectiousness), was recorded in 11 of the first 53 positive cases of the outbreak at diagnosis. Second, HTD offices are typically equipped with air conditioners without mechanical ventilation systems, a well-known indoor setting that could facilitate the transmission of SARS-CoV-2. Third, mask wearing in the office was not mandatory at the time.
Lower levels of neutralizing antibodies after vaccination and at diagnosis were associated with breakthrough infections in a recent report from Israel, supporting findings of the present study. However, we found no correlation between vaccine-induced neutralizing antibody levels at diagnosis and the development of respiratory symptoms or viral loads (i.e. infectivity). Thus, while neutralizing antibodies might be a surrogate of protection, especially against severe diseases as a whole, they might not be good indicators ofdisease progression and infectiousness for breakthrough Delta variant infection. The rapid increase in neutralizing antibodies after infection among cases of the present study in turn suggested that a third dose may improve the immunity and potentially the protection. At the beginning of the outbreak, none of the HTD members of staff (including the PCR confirmed cases) were tested positive for N-protein antibodies, which only develop in response to whole-virus based vaccine and natural infection. Additionally, between 12th and 14th May 2021, all members of HTD staff were subjected to a periodic testing for288SARS-CoV-2 by PCR, but none was positive. The data thus suggested that the infected cases were captured at an early phase of the infection. Therefore, by carefully following up the patients during hospitalization, we have also provided new insights into the natural history of breakthrough Delta variant infections. We found viral loads of breakthrough Delta variant infection cases peaked around 2-3 days before and after the development of symptoms, and were 251 times higher than those of the infected cases detected during the early phase of the pandemic in 2020. Additionally, there has been only one report showing that 9/11 cases of vaccine breakthrough infection had no detectable RNA when retested within 2–7 days after diagnosis. Yet, we found prolonged PCR positivity was up to 33 days in our study participants. These factors might explain the current rapid expansion of the Delta variant, even in the countries with high vaccination coverage.
In summary, we report the transmission SARS-CoV-2 Delta variant among vaccinated health care workers. Breakthrough Delta variant infections are associated with high viral loads, prolonged PCR positivity, and low levels of neutralizing antibodies after vaccination and at diagnosis. These factors coupled with poorly ventilated indoor settings and without mask wearing might have facilitated presymptomatic and/or asymptomatic transmission among the vaccinated workers. Physical distancing measures remain critical to reduce SARS-CoV-2 Delta variant transmission, thereby mitigating the impact of the ongoing COVID-19 pandemic."
