The 2019-20 coronavirus disease, caused by COVID-19, is an ongoing pandemic. The outbreak
started in Wuhan, Hubei province, China, in December 2019 and the World Health Organization
(WHO) recognized it as a pandemic on 11 March 2020. Up to Apr 9. 2020 there are more than 1.4
million confirmed cases, and over 82,000 deaths 1. In Israel, COVID-19 was confirmed in more
9,000 cases and took the life of 70 victims (09.04.2020) .

With the extensive outbreak of COVID-19, a mass of studies with a large population have been
reported. Wu et al. found that the mean R0 of COVID-19 was approximately 2.68(95% CI:
2.47-2.86) . The measures in which public health officials quarantine confirmed and isolate
symptomatic cases in order to reduce the spread COVID-19 is the common practice used in most
countries. However, a significant question remains in regards to the asymptomatically
infected individuals, which may propagate the virus and impede infection control.

The problem To date, initial surveillance has focused primarily on patients with severe
disease, and, as such, the full spectrum of the disease. The extent of asymptomatic disease
is not clear. Mizumoto et al. mathematical model suggested 17.9-33.3% are asymptomatic
carriers. The other question to consider is whether these asymptomatic carriers develop an
immune response or continue viral shedding.

SARS-CoV-2, the causative viral agent of the disease COVID-19, is a coronavirus which bears
the transmembrane glycoprotein spikes (S protein) typical of viruses in its clade. The spikes
on SARS-CoV-2 allows the virus to enter host cells through the human receptor angiotensin
converting enzyme 2 (ACE2), present in alveolar epithelial cells. These spikes are a
prominent target of human immune responses and have been found to be highly immunogenic and
induce antibody production. The receptor-binding domain (RBD) of the S protein is
particularly targeted by neutralizing antibodies.

The diagnostic test in symptomatic patients is based on real time polymerase chain reaction
(RT-PCR), which tests the existence of specific COVID-19 genes in the sample. However, there
are growing numbers of reports of false negative results due to improper sample collection,
low viral load or technical instability of the PCR.

Serology test aims to detect antibodies (immunoglobulin M - IgM, immunoglobulin G- IgG,
immunoglobulin A - IgA) in the patient's' blood, i.e. the patient's immune response. The IgM
antibodies usually show within 3-7 days from symptoms, whereas IgG antibodies follow within
10-14 days. Diseases which involve the respiratory tract usually cause elevation of IgA as
well.

Zhao et al. have recently published data indicating that COVID-19 patients show typical
antibody production times in response to acute viral infection with SARS-CoV-2. Overall, the
data suggest that SARS-CoV-2 infection follows a seroconversion timeline similar to other
viral infections. In their sample of 173 of hospitalized symptomatic confirmed patients,
93.1% (161/173) developed antibodies, where 82.7% developed IgM antibodies and 64.7%
developed IgG antibodies. Importantly, all of these patients suffered from symptoms. The
association between symptoms level, viral load and the immune response is yet to be
determined.

Closed settings, such as households, have a defined population that may not mix readily with
the larger surrounding community, and therefore such settings can provide a strategic way to
track emerging respiratory infections and characterize virus transmission patterns because
the denominator can be well defined. Also, exposure is within the setting, and follow-up of
household contacts is generally more feasible in this well-defined setting as compared to an
undefined one. Following close contacts with similar levels of exposure to infection from
primary cases can also permit identification of the asymptomatic fraction.

Our solution The purpose of the current study is the evaluate the immune response, i.e
developing anti-SARS-CoV-2 antibodies in the asymptomatic cases, in a household study design.

We plan to evaluate over 1000 patients with positive COVID-19 results and their households.
The plan includes evaluation of their symptoms, viral load and immune response every 10 days
in a period of 12 weeks. Next, Analysis of the cause of the immune response differences
between subjects by sequencing their DNA and most importantly of the ACE2 gene - the receptor
the virus attacks.

This will shed the needed light on the connection between symptoms, viral load and immune
response. The association between viral load, symptoms and immune response will enable:
monitor disease progress, predict patients who are at high risk to develop severe symptoms,
determine immunity to the virus and most importantly locate the chronic carriers which do not
develop immunity.

Protocol Following a positive COVID-19 RT-PCR result in the Shamir medical center lab, the
subject will be contacted by telephone and will be offered to participate in the study. Upon
consent, medical staff will arrive to the subject's house and further explain the details of
the study and ask for an informed consent of the subject and any of the households over 18
years old. Upon signing an informed consent, each of the subject will fill a symptoms report
and provide an oropharyngeal swab and blood sample (10-20cc).

Every 10 days within 12 weeks, a researcher will visit the subjects house, and repeat the
procedure (symptoms questionnaire, blood withdrawal and oropharyngeal swab).

Following the last evaluation (12th week), every 4-8 weeks within 1 year, a researcher will
visit the subjects hosue and perform filling of symptoms questionnaire and blood withdrawal.

Serology kits:

1. LIAISION SARS-CoV-2 IgM (Diasorin, Saluggia, Italy)

2. LIAISION SARS-CoV-2 S1/S2 IgG (Diasorin, Saluggia, Italy)

3. ARCHITECT SARS-CoV-2 N IgG Immunoassay (Abbot, Illinois, U.S.A)

Rt-PCR kit RT-PCR will be performed using 3 primers and 3 probes in addition to one human
RNase primer and probe.

Procedure

1. Arrival to the subjects house

2. Medical staff will use appropriate protective medical gear.

3. Blood withdrawal for 3 blood tubes (15-20cc)

4. Oropharyngeal swab

5. Samples will be kept at 2-8c degrees.

6. Samples will be returned to Shamir Medical Center lab in 2-8c degrees.

7. RT-PCR will be performed.

8. Serology will be performed using the available kits. Each subject will be sampled 9
times (every 10 days within 12 weeks in addition to the first contact). Blood samples
will be kept and stored at -80°C for future research purposes.

Long term evaluation will include Blood sample and questionnaires every 4-8 weeks for 1 year
from the final evaluation (12th week).

Timing

1. The first evaluation will be completed for both the patient and his/her households
within 1-7 days of receiving the RT-PCR positive result

2. Following the first evaluation, each participant will be evaluated every 10 days (±2
days) for 100 days. In total 10 additional times.

In summary, each participant will be evaluated 11 times (first evaluation + 10
additional evaluations).

3. Following the last evaluation, each participant will be evaluated every 4-8 weeks for 1
year. In total 6-12 times.