Investigators have demonstrated the in vitro viridical efficacy of both Listerine
Antiseptic® and 1% dilute baby shampoo solution, a commonly used nasal rinse, against a
SARS-CoV-2 surrogate and Meister et al. have similar findings with SARS-CoV-2. With an
urgent need to expand the armamentarium of widely available, low-cost interventions, that
are safe for repeated human use and reduce viral transmission, investigators seek to
determine the impact of a combined regimen of oral and nasal rinsing with these agents on
naso-oropharyngeal viral loads in adults (aged 18-65 years) with SARS-CoV-2 infection.

Rationale for the intervention: a combination of nasal washes with 1% solution of baby
shampoo and oral washes with Listerine Antiseptic® Available data indicate that
SARS-CoV-2 is most likely to spread, like most other common respiratory viruses,
primarily through respiratory droplet transmission. With the naso-oropharynx being both
the primary site from which the virus is expelled by people with infection and the nasal
and oral mucosal cells is one of the sites of initial infection and viral replication.
Specifically the ACE2 receptor, that SARS-CoV-2 binds for cell entry, are highly
concentrated in the goblet and ciliated cells of the nose and on the tongue. Thus a
reduction of viral load through topical treatment of these sites could potentially lead
to reduced transmission of SARS-CoV-2.

Each of the two proposed agents to be tested have independently demonstrated virucidal
activity with short contact time in vitro. With over 140 years of usage worldwide, the
safety of gargles with Listerine Antiseptic® is well established. Topical nasal lavage
using a dilute solution of baby shampoo has also been demonstrated to be safe and
effective both as a mucoactive and microbicidal agent. Both agents are readily available
and cost-efficient for daily usage.

While there are a number of ongoing trials of interventions with similar approaches, most
of them focus on a single intervention, either nasal or oral rinses. This potentially
leaves a viral reservoir in the untreated site, with the potential for recolonizing the
entire oronasopharynx thereby limiting the utility of intervention. There is a single
trial treating both the oral and nasal spaces. However, the agent being tested is
povidone-iodine, that has known adverse effects limiting its use. These adverse effects
include discoloration of teeth, ciliary dysfunction, iodine overdose and possible drug
interactions, such as with lithium.

Investigators believe that the proposed intervention for this study is likely to be
well-tolerated, highly acceptable and result in elimination from the key sites in the
oronasopharynx. Additionally, the proposed four-arm design will allow investigators to
compare the combined intervention with each of the component treatments. A decision was
made to use saline rinses as the control arm as the investigator's in vitro data revealed
that saline had no virucidal activity against human coronavirus.

Based on recent literature describing viral load dynamics during the course of SARS-CoV-2
infection, investigators believe that a four-day trial, initiated within 5 days of Covid
testing, will allow for the testing of change in viral load close to/or within the 7-10
day timeframe of greatest SARS-CoV-2 viral load. The study period will also fall within
the 2-3 week period of the mean duration of SARS-CoV-2. Mohamed et al suggest that 4 days
of oral Listerine washes three times daily may be efficacious in decreasing viral load.
Several other rinse trials also employ this rinse frequency. The rinse times of 60 secs
and 30 secs for nasal wash with 1% dilute baby shampoo and oral Listerine respectively,
are based on the successful virus reduction demonstrated at these contact times in vitro.