Today we have updated two evidence summaries on COVID-19, one of which examines the immune response following infection and another which looks at the viral load and infectivity over the course of infection.
These evidence summaries have been updated to include new studies which have been published since the original reviews.
Our updated evidence summary on the immune response following an infection with SARS-CoV-2 examined over a 100 studies to assess the antibody response following coronavirus infections and the potential for reinfection following recovery. However, the evidence in this area remains inconclusive. SARS-CoV-2 is a new virus. While the detection rate and timing of antibodies following SARS-CoV-2 infection varied across studies, all patients eventually mounted an antibody response. The long-term duration and the adequacy of this response is not yet known as the longest follow-up was eight weeks. It is not yet known if reinfection with SARS-CoV-2 is possible. While there have been cases of people testing positive for SARS-CoV-2 following recovery, these may be ‘re-detection’ cases as opposed to reinfection. Nearly all patients who were ‘re-detected’ did not show symptoms or disease progression. Our updated evidence summary on the immune response examined over a 100 studies to assess the antibody response following coronavirus infections and the potential for reinfection following recovery.
HIQA will present this evidence summary to members of the EU/EEA National Immunisation Technical Advisory Group (NITAG) Collaboration on Immunity to SARS-CoV-2 this week by video link to a meeting organised by the European Centre for Disease Control (ECDC).
Our updated viral load and infectivity evidence summary, which also included over 100 studies examined the viral load of SARS-CoV-2 over the course of the infection and found the new evidence to be broadly consistent with our previous findings. In general, SARS-CoV-2 viral levels were found to peak around symptom onset or a few days after, and become undetectable about two weeks after symptom onset, when respiratory tract samples are tested. The virus may be detected for longer periods in stool samples; however, it is still unknown whether the virus can be spread from the stools of infected patients. It is also unclear how long patients with COVID-19 remain infectious, although there is evidence that patients may not be infectious for the entire duration that the virus is detectable. Patients appear to be most infectious near, or even before symptom onset, when the viral loads are highest.
HIQA’s Deputy CEO and Director of Health Technology Assessment, Dr Máirín Ryan, said: “These evidence summaries showcase the importance of further research in the areas of SARS-CoV-2 infectivity and immunity. Establishing the duration of both of these is vital, as it is key to informing public health policy in managing the pandemic.”
To support effective public health decision-making in response to the outbreak, we have developed, and continue to update, nine evidence summaries of international literature on COVID-19 so far. Other evidence summaries are in development and will be published soon. The research answers questions posed by the National Public Health Emergency Team’s Clinical Expert Advisory Group.
So far, we have published summaries answering the following questions:
- What is the evidence for asymptomatic transmission of COVID-19?
- What is the viral load over the course of the infection (including any asymptomatic or pre-symptomatic phase), and the duration of infectivity?
- What evidence is available to indicate that children spread COVID-19?
- What is the natural history of COVID-19 infection in children?
- What is the average length of stay in intensive care (ICU) for affected persons?
- For individuals who have COVID-19, what clinical samples and collection sites are suitable for SARS-CoV-2 testing?
- Are individuals reinfected with SARS-CoV-2 or other human coronaviruses infectious?
- Is there evidence for placental transfer of antibodies, from infected mothers, that confers immunity in the newborn?
- What is the rate of reinfection/duration of immunity in individuals who recover from a laboratory-confirmed coronavirus infection?
Dr Ryan said: “Each summary is developed following a thorough search of bibliographic databases, screening of identified studies to match relevant clinical questions, data extraction and appraisal of included studies.
“We are also continuing to assist evidence-based decision-making through conducting rapid reviews and updating a database of public health guidance on a daily basis. In addition, we conducted a rapid health technology assessment of alternative diagnostic testing for SARS-CoV-2.”
Read the evidence summaries here.