Delta (B.1.617.2), Vaccine Effectiveness & Intranasal Vaccines: Microbial Minutes
Are breakthrough infections more common with Delta? Why are fully vaccinated people still transmitting the virus? Could intranasal vaccines block transmission? What can be done to stop viral evolution?
What's Hot in the Microbial Sciences?
ASM presents Microbial Minutes, a monthly video series of trending topics in the microbial sciences.Recent surges of COVID-19 as a result of the Delta variant’s rapid spread have caused mixed feelings of discouragement, fear and denial across the globe. Healthcare workers are once again feeling the strain as hospitals are flooded with COVID-19 cases. And the CDC has recommended masking in indoor public spaces, regardless of vaccination status, in areas where COVID-19 transmission is high.
People are questioning whether vaccines are still working. And if so, why we need to wear masks again. We dissect the research that will help address those questions.
Will Vaccines Remain Protective Against the Delta Variant?
How Dangerous is the Delta Variant (B.1.617.2)?Stowe J. et al. "" 2021
Venkata-Viswanadh E. et al. "Infection and Vaccine-Induced Neutralizing-Antibody Responses to the SARS-CoV-2 B.1.617 Variants."
Are Breakthrough Infections More Common With Delta?
Gupta N. et al. "Clinical characterization and Genomic analysis of COVID-19 breakthrough infections during second wave in different states of India."
Brown C.M. et al. "Outbreak of SARS-CoV-2 Infections, Including COVID-19 Vaccine Breakthrough Infections, Associated with Large Public Gatherings — Barnstable County, Massachusetts, July 2021."
Why Are Fully Vaccinated People Still Transmitting the Virus?
Ying Chia P. et al. "Virological and serological kinetics of SARS-CoV-2 Delta variant vaccine-breakthrough infections: a multi-center cohort study."
Matheson N.J. et al. "How does SARS-CoV-2 cause COVID-19?"
Sheikh-Mohamed S. et al. "A mucosal antibody response is induced by intra-muscular SARS-CoV-2 mRNA vaccination."
Could Intranasal Vaccines Help Block Transmission?
van Doremalen N. et al. "Intranasal ChAdOx1 nCoV-19/AZD1222 vaccination reduces viral shedding after SARS-CoV-2 D614G challenge in preclinical models."An D. et al. "Protection of K18-hACE2 mice and ferrets against SARS-CoV-2 challenge by a single-dose mucosal immunization with a parainfluenza virus 5–based COVID-19 vaccine."
Take-Away Points
- The Delta variant is 40-60% more transmissible than Alpha and almost twice as transmissible as the original Wuhan strain.
- Vaccines remain highly effective at preventing hospitalization and death from Delta infection.
- Data indicate that vaccinated individuals may still be able to transmit the virus.
- This is due, in part, to the generation of insufficient mucosal immunity via systemic injection to remain protective long term.
- Mucosal routes of immunization are under investigation, with a number of intranasal vaccines entering clinical trial.
- In combination, vaccination and masking can reduce the risk of severe disease, slow transmission and reduce the evolution of SARS-CoV-2.
