THE Joint Committee on Vaccination and Immunisation (JCVI) is advising that people with severely weakened immune systems should have a third vaccine dose as part of their primary Covid-19 vaccination schedule.

This third dose should be offered to people over 12 who were severely immunosuppressed at the time of their first or second dose, including those with leukaemia, advanced HIV and recent organ transplants.

These people may not mount a full response to vaccination and therefore may be less protected than the wider population.

This offer is separate to any potential booster programme. The JCVI is still deliberating the potential benefits of booster vaccines for the rest of the population and is awaiting further evidence to inform this decision.

Immunosuppression varies widely in severity and duration. Many people who are immunosuppressed have lower levels of antibodies after Covid-19 vaccination, as some studies have shown.

Preliminary data from the OCTAVE trial showed that almost everyone who was immunosuppressed mounted an immune response after two doses, as indicated by either antibodies or T cells. However, in around 40% of people, the levels of antibodies were low. It is not clear how much this may affect protection against Covid-19 as antibodies represent only part of a person’s immune response.

People with severe immunosuppression are more likely to be severely ill if they do catch Covid-19.

Health and Social Care Secretary Sajid Javid said: “Today I have accepted the expert recommendations from the independent Joint Committee on Vaccination and Immunisation to offer a third vaccine dose to people aged 12 and over with severely weakened immune systems as part of their primary schedule following data from trials of those who are immunosuppressed.

“We know people with specific conditions that make them particularly vulnerable to Covid-19 may have received less protection against the virus from two vaccine doses. I am determined to ensure we are doing all we can to protect people in this group and a third dose will help deliver that.

“The NHS will contact people as soon as possible to discuss their needs and arrange an appointment for a third dose where clinically appropriate.

“This is not the start of the booster programme – we are continuing to plan for this to begin in September to ensure the protection people have built from vaccines is maintained over time and ahead of the winter. We will prioritise those most at risk to Covid-19, including those who are eligible for a third primary vaccine, for boosters based on the final advice of the JCVI.”

Studies are ongoing to see how effective a third dose is for immunosuppressed people, but it is very unlikely to cause any harm. Therefore, on balance, the JCVI’s view is that a third dose can be safely offered as it may increase their protection.

Professor Wei Shen Lim, Chair of Covid-19 Immunisation for the JCVI, said: “We want people with severely suppressed immune systems to have the best chance of gaining protection from Covid-19 via vaccination. Therefore, we are advising they have a third vaccine dose on top of their initial two doses, as we hope this will reduce their risk of severe outcomes such as hospitalisation and death.”

The JCVI advises that for adults aged 18 and older, either the Moderna or Pfizer-BioNTech Covid-19 vaccines be administered for the third dose, as a number of studies have reported an increased immune response in some immunosuppressed people after a third dose of an mRNA vaccine. For those aged 12 to 17, the Pfizer-BioNTech vaccine is preferred.

A third primary dose is an extra ‘top-up’ dose for those who may not have generated a full immune response to the first two doses. In contrast, a booster dose is a later dose to extend the duration of protection from the primary course of vaccinations.