Coronavirus disease (COVID-19) technical guidance by WHO Household transmission investigation protocol | Page 22

Serological response
to infection. Change in serum level of
specific antibodies to
COVID-19 virus. (Increase
in titre). Laboratory results
Incubation period The period of time between
an exposure resulting in
COVID-19 infection and the
appearance of the first sign
or symptom of the disease.
(From infection to disease) Date of onset of
symptoms and
dates of contact
with confirmed
case.
Serial interval The period of time from the
onset of symptoms in the
primary case to the onset of
symptoms in a contact.
(From clinical onset to
clinical onset).
Form 2, 3, 4, 5
Generation time
distribution. The time between infection
in the case and infection in
the household contact.
(From infection to infection)
Population groups
most at risk Determination of the groups
that are most vulnerable to
infection with COVID-19
(e.g. age groups, sex,
occupation).
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Symptom diary
Symptoms and
dates.
Form 1A: Q6
Form 1B: Q6
Form 2, 3, 4, 5
Symptom diary
Specimens and
dates
Form 1 Q5
Form 2, 3, 4, 5
Demographic data
Form 1A: Q4, Q5
Form 1B Q4, Q5
• It will only be possible to
calculate this with the
addition of laboratory
data.
• Will be supplemented by
the findings of clinical
studies and investigations
of the first few
outbreaks, to confirm
that seroconversion
following an infection is
anticipated.
• Will be greatly enhanced
by information from the
first few outbreaks,
where transmission
chains may be more
identifiable and
prolonged.
• Will be greatly enhanced
by information from the
first few outbreaks,
where transmission
chains may be more
identifiable and
prolonged.
• May only be an early
signal; other sources of
information will need to
be used to inform
decision-making (line
listing of cases and other
clinical case-series).
• This may be biased from
this study, as recruitment
is on the basis of being
detected and confirmed
to have COVID-19 and
health-care-seeking
behaviour may vary
between population
groups.