People can rarely be reinfected with different strains of Covid-19 but it does mean immunity cannot be assumed by people how have had the disease, the public and those responsible for managing prevention and developing vaccines, according to the the Health Information and Quality Authority (HIQA).
The Authority has published advice which it says it has submitted to Dr Tony Holohan and the National Public Health Emergency Team (NPHET) to support the team's ongoing response to Covid-19 or SARS-CoV-2.
In a statement, HIQA says it previously published evidence summaries on many aspects of the immune response following SARS-CoV-2 infection. In this update, HIQA says has reviewed new evidence relating to the possibility of reinfection following recovery from the virus. It says it has also looked at studies with longer follow-up looking at the duration of immunity following infection.
Dr Máirín Ryan, HIQA’s Deputy CEO and Director of Health Technology Assessment outlined the findings.
“New evidence has demonstrated that reinfection can occur following recovery from SARS-CoV-2 infection. Worldwide, at least fourteen patients have been infected twice by SARS-CoV-2; these reinfections were confirmed by genetic evidence that showed the first and second infections were caused by different viral strains. It is important to remember, however, that these are rare events.
“The phenomenon of reinfection has significant policy implications. Infection prevention and control, isolation and contact tracing considerations are not likely to differ for cases of reinfection compared with the first infection. Therefore, all public health advice, including hygiene and physical distancing, should apply to those who have recovered from a SARS-CoV-2 infection as immunity from reinfection cannot be assumed.”
Dr Ryan said the evidence summary also reviewed the current evidence on the maximum duration of immunity following infection.
“Evidence from 22 studies suggests that IgG antibody levels (the most common antibody in the blood) are sustained for at least two months after infection, and for some even up to six months. The levels of neutralising antibodies (that can neutralise viruses like SARS-CoV-2), decline over time, especially in the later stages of follow-up," she said.
Pfizer has announced that it has a vaccine that is 90% effective but HIQA says the evidence about reinfection has implications.
"While this doesn’t offer a full picture of the body’s response to SARS-CoV-2, these data have implications for vaccine development, antibody testing and immunotherapy going forward,” she said.
HIQA says many current vaccine design efforts focus on generating a strong neutralising antibody response to provide protection from infection. The Authority says its findings of a reduction in neutralising capacity over time suggests immunity may not be long-term.
"If vaccination results in a similar response, consideration may be given to the need for repeat or ‘booster’ doses," said HIQA .
HIQA also published a scoping evidence review on convalescent plasma therapy conducted at the request of the Department of Health. This scoping review looked at the use of convalescent plasma as a potential treatment for patients with COVID-19, experiencing, or who are at risk of experiencing, a severe course of the disease.
Since September 2020, HIQA has provided evidence-based advice in response to requests from NPHET.
HIQA says its advice to NPHET is informed by research evidence developed by HIQA’s COVID-19 Evidence Synthesis Team, with expert input from HIQA’s COVID-19 Expert Advisory Group.
The topics HIQA researches are outlined and prioritised by NPHET to ensure that they have rapid access to the best available evidence relevant to the Covid-19 outbreak.
HIQA’s says its Covid-19 Expert Advisory Group is a multidisciplinary group, comprising nominated representatives from the relevant clinical specialties and areas of expertise, methodology experts, and public representation.
The latest documents published today are available here.