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The Health Protection Surveillance Centre (HPSC) has said individuals vaccinated against Covid-19 and who are identified as close contacts of confirmed cases need not be tested or restrict their movements in most cases.
Specific definitions on who are considered to be vaccinated individuals is provided in new contact tracing guidance published on 6 May.
They include individuals who are seven days in receipt of their second Pfizer-BioNTech dose, persons 14 days in receipt of their second Moderna dose, people 14 days after receiving their one-short Janssen dose and individuals 28 days in receipt of their first AstraZeneca dose.
According to guidance, a vaccinated close contact will only be tested if a case is linked to a confirmed or probable variant of concern, or if they develop symptoms of Covid-19.
“If the test result is negative they can discontinue self-isolation once they are symptom free for 48 hours,” guidance states.
Testing of vaccinated close contacts may also occur if a person’s immune system is compromised “due to either a known medical condition or being on immunosuppressive treatment”.
“If there is any uncertainty as to whether the close contact has a medical condition or takes a treatment that would result in a sub-optimal response to vaccination, they should also be advised to restrict their movement and contact their treating physician who can advise if these recommendations apply to them.”
Vaccinated individuals may also require testing if a public health or occupational health risk assessment identifies that they are a close contact of a case linked to an outbreak.
Separate guidance for healthcare workers states that close contacts who have completed vaccination do not need to restrict movements or receive follow-up for cases excluding variants of concern.
Research on whether or not a fully vaccinated individual can transmit the virus to others is “scarce” because most vaccine effectiveness studies were not designed to measure transmission risk.
A study in Scotland that found the risk reduction of virus transmission in those who have been vaccinated could be as high as 60 per cent, according to guidance.
Furthermore, an European Centre for Disease Control (ECDC) report in April concluded that “based on the limited evidence available the likelihood of an infected vaccinated person transmitting the disease is currently assessed to be very low to low”.
But the HPSC guidance advises that “Covid-19 vaccines do not confer sterilising immunity to all individuals and therefore vaccinated individuals might still be able to transmit SARS-CoV-2 infection to susceptible contacts”.