On June 11, 2021, a 41-year-old staff member of the Hospital for Tropical Diseases (HTD) in Ho Chi Minh City in Vietnam complained of body pain and tiredness and tested positive for SARS-CoV-2.
The testing was expanded to all hospital staff and was completed by June 12, 2021. An additional 52 members were found positive.
Following Vietnamese government regulations, the HTD was locked down from June 12-26th, 2021. No one was allowed to leave the hospital. Further testing on all staff identified 16 additional cases.
This brings the total to 69 infected members from 19/34 departments. Sixty-two consented to have their demographics reported. Among them, two received one dose of vaccine, and 60 were fully vaccinated. All received the Oxford Astra-Zeneca vaccine, and all recovered fully.
While in lockdown, the patients were clinically followed, serial PCR testing and antibody titers were observed.
The PCR was done until the test was negative.
Results:
Viral loads
The peak viral loads of breakthrough cases were 251 times higher compared to the viral loads among unvaccinated SARS-CoV-2 patients between March and April 2020.
The mean time for the PCR test to be negative is 21 days from the initial positive test, and the longest positivity is 33 days.
Delta Variant
Genome sequencing of the SARS-CoV-2 among the subjects showed the Delta variant, which differs from the Delta variant in the community. The authors conclude that the healthcare workers are transmitting the Delta variant within the hospital.
Antibody levels
All but 3 had detectable neutralizing antibody levels with comparable levels between (pre)symptomatic and symptomatic cases.
Likewise, there was no correlation between neutralizing antibodies at diagnosis and peak viral loads during the course of the infection.
Implications of the Study according to the authors
Our study provided strong evidence demonstrating for the first time the transmission between vaccine breakthrough cases infected with the delta variant.
High viral loads coupled with prolonged PCR positivity and poorly ventilated indoor setting without office mask wearing might have faciliatated the trasmission between vaccinated healthcare workers.
The absence of correlation between neutralizing antibody levels and peak viral loads suggested that vaccine might not lower the infectivity of breakthrough cases.
The other significance was the prolonged PCR positivity of up to 33 days. This might explain the rapid spread of the Delta variant even in countries with high vaccination coverage.
What makes the Delta variant more infectious?
The Delta variant possesses mutations in the spike protein (including L452R and T478K) that make the virus less susceptible to neutralizing antibodies generated by the current vaccines or natural infection.
In a study published in Cell Host and Microbe, “the L452R mutation increases spike stability, viral infectivity, viral fusogenicity, and thereby promotes viral replication.”
The T478K mutation is structurally located in the region of the spike protein that interacts with the human receptor ACE2. An antibody developed against the usual spike protein will not recognize the mutation’s new antigen configuration.
Take Away Message:
The vaccinated can still harbor the Delta variant and potentially spread it to others. Mask and handwashing remain essential.
The SARS-CoV-2 can be present in the nose for as long as 33 days.
The FLCCC developed a COVID-19 prevention protocol. You can find it here: An update to the I-MASK+ Prevention & Early Outpatient Treatment Protocol for COVID-19.
This study is consistent with the Israel study presented in, Who develops a better Immunity against SARS-CoV-2? The vaccinated or the previously infected?
Knowledge about Covid-19 is rapidly evolving. Information may update as new studies are made. Stay current by subscribing. Feel free to share and like.
Don’t Get Sick!
References:
- Chau et al. Transmission of SARS-CoV-2 Delta Variant Among Vaccinated Healthcare Workers, Vietnam. https://ssrn.com/abstract=3897733 or http://dx.doi.org/10.2139/ssrn.3897733
- Motozono et al. SARS-CoV-2 spike L452R variant evades cellular immunity and increases infectivity. Cell Host Microbe. 2021 Jul 14;29(7):1124-1136.e11. doi: 10.1016/j.chom.2021.06.006. Epub 2021 Jun 15. PMID: 34171266; PMCID: PMC8205251.
- , , and . Preliminary report on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Spike mutation T478K. J Med Virol. 2021; 93: 5638– 5643. https://doi.org/10.1002/jmv.27062
Image credit: SARS-CoV-2 mutations By Stanford HIVDB Team, Philip – https://covdb.stanford.edu/page/mutation-viewer/, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=106842398
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