Thread by @DrEricDing

📍A revealing outbreak among gold miners infected with #P1 #GammaVariant in French Guiana—55% of 44 infected—no severe but 87% symptomatic—65% fever, 22% difficultly breathing. Attack rate was 60% in fully Pfizer-vaccinated, 75% in unvaccinated miners.🧵
wwwnc.cdc.gov/eid/article/27…

2) It all likely started with an asymptomatic index case… “Patient 40 could be the index case-patient; he reported visiting his family the previous week and had an asymptomatic SARS-CoV-2 infection with Ct of 33–35.” 👀—a very low viral load index that triggered the cluster!

3) Any vaccine cold chain break? No. “Several BNT162b2 batch numbers were involved. Vaccine temperature had been monitored and electronically recorded by LogTag Analyzer (LogTag Recorders, logtag-recorders.com) without any break in the cold chain.”

4) Mine workers mostly men (42/44); median age 53.3. 18 of the workers had risk factors: high blood pressure (11/44), diabetes mellitus (4/44), or obesity (4/44). Miners lived onsite in separate rooms but shared meals and machine cabins. They also worked outside without masks.

5) “However, other VOC, such as Beta or Gamma, harbor mutations conferring potential escape from humoral response induced either by prior infection or vaccination, as proven by both decreased seroneutralization in vitro (5–7) and in vivo by observational studies”

6) #P1 #GammaVariant is the main variant that ravaged Brazil 🇧🇷 previously. It is also the predominant variant in French Guiana (just north of Brazil), where it is causing hospitalization surges. guyane.ars.sante.fr/system/files/2…

7) authors: “Such a low vaccine efficiency against infection by the #Gammavariant was not expected because in vitro studies have shown a similar reduction of neutralization for Beta or Gamma variants by BNT162b2-elicited antibodies” pubmed.ncbi.nlm.nih.gov/33794143

8) “Given the surprisingly high attack rate, we hypothesized potential dysfunctions of conservation or administration of vaccines, but the absence of traceable cold-chain interruption and the use of different batches seemed to refute this hypothesis.” (Not cold chain issues)

9) “The relative isolation of the mining site and careful contact tracing suggested limited numbers of viral introductions inside this community.” (the outbreak was isolated among local miners, not due to outside community spread).

10) “The low Ct of positive PCR (high viral load) despite prior vaccination suggested that a complete vaccination scheme with BNT162b2 vaccine was not sufficient to prevent symptomatic SARS-CoV-2 infection and its transmission in this communal life without masks.” ➡️MASKS needed.

11) “The working conditions of some miners (heat, humidity, aerosol) and the sharing of machine cabs for others could also have contributed to transmission” ➡️ we need ventilation or air disinfection too.

12) “Our observation suggested that BNT162b2 protected from severe COVID-19. However, this single unexpected outbreak in a small and isolated vaccinated population requires further real-life studies on BNT162b2 vaccine effectiveness against the VOC Gamma.

13) “Masking and social distancing —even among those fully vaccinated— may be necessary among persons with frequent exposure in Gamma variant–endemic zones.”

14) A good thread on breakthroughs from @Survivor_Corps — there is LongCOVID even among breakthrough.

https://twitter.com/dianaberrent/status/1418234003640000519

15) Great piece on understanding breakthrough infections by @apoorva_nyc. Vaccines work but not perfectly for milder infections - hence we need to mask and ventilate. nytimes.com/2021/07/22/hea…