Throughout the pandemic, the Joint Committee on Vaccination and Immunization (JCVI) provided advice to the UK government on COVID-19 vaccination, with the main aim of reducing serious illness (hospitalization and mortality) in the population. COVID-19 disproportionately affects people in older age groups, residents of elderly care homes, and people with certain underlying health conditions (people in clinical risk groups). For this reason, these groups have been prioritized for immunization in all countries. JCVIadvice from.

Adult program overview

In December 2020, JCVI advised phase 1 of the COVID-19 vaccination program to offer a primary vaccination comprising 2 doses of vaccine to people aged 50 years and over, and to those in clinical risk groups, with priority given to those most at risk of serious illness. Before the completion of phase 1 (in April 2021), JCVI issued a final opinion on phase 2 of the vaccination program for all adults aged 18 to 49 who had never received a vaccine before. Phase 2 aimed to further reduce morbidity from COVID-19 in the population.

In June 2021, JCVI issued an interim opinion on a recall program, aimed at maintaining protection against COVID-19 until winter 2021 to 2022 and until 2022. This notice was finalized in September 2021, setting the priority for the booster vaccination starting with the most vulnerable in the UK population; specifically all adults aged 50 and over, and those in clinical risk groups. The booster vaccination was scheduled for 6 months after the end of the primary vaccination course based on the evidence of some decreased protection against severe disease caused by the wild-type virus and existing variants of concern, including Alpha and Delta, in the elderly 6 months after the primary vaccination. Delivery of the recall program began immediately after the publication of the notice.

In November 2021, once substantial progress has been made in providing booster doses to those most vulnerable to severe disease (the elderly and clinical risk groups), JCVI advised extending the booster program to people aged 40 to 49, with the aim of further increasing the population’s immunity to morbidity and mortality from COVID-19.

On November 26, 2021, the World Health Organization classified a new variant, the Omicron, which was spreading rapidly in a number of countries. The Omicron variant is important for the many mutations affecting the spike protein versus the wild-type viral protein upon which existing COVID-19 vaccines are based. In response to the Omicron threat, on November 29, 2021, JCVI advised both the extension and the acceleration of the booster vaccination program; to advise :

  • all adults aged 18 and over are offered a booster vaccination in descending order of age
  • a reduction in the interval between the primary vaccination and the booster from 6 to 3 months

Figure 1: Eligibility and coverage of the recall program since September 2021 over time

Boost the effectiveness of the program

So far, the booster program has provided high levels of protection against serious illnesses due to COVID-19 (Delta and Omicron variants) across the population. The latest data from the UK Health Security Agency (UKHSA(see COVID-19 vaccination effectiveness monitoring reports). These data underscore the importance of the booster vaccination and the additional protection achieved against the Omicron variant.

Ongoing review of new booster doses

In view of the obvious importance of the booster vaccination in the protection against severe disease of Omicron, JCVI reviewed the potential health benefits of an immediate additional booster dose for the most vulnerable people in society in response to the current wave of Omicron. Right now, JCVI indicates that the priority of the COVID-19 booster program remains increasing coverage of the first booster dose in the adult population, particularly in the elderly and those belonging to clinical risk groups. In addition, it is important that unvaccinated individuals, especially vulnerable adults, receive a primary cycle of vaccination, regardless of whether the individuals have been previously infected.

In his review, JCVI consider that :

  • the booster program, which began in September 2021, still offers very good protection against severe disease, including in the elderly (see COVID-19 vaccination effectiveness monitoring reports)

  • an immediate second booster dose of the vaccine in the most vulnerable (those over 80 years of age or in a nursing home for the elderly) would provide only limited additional benefit against severe disease at present

  • a second immediate recall program for the most vulnerable would add to significant operational pressures existing for the rest of the COVID-19 vaccination program and other health services

  • the current wave of Omicron is advancing very rapidly, providing limited time for additional measures of the immunization program to have a substantial impact within this wave

  • the main objective of the vaccination program remains the prevention of serious diseases; protection against mild or asymptomatic infection with existing vaccine products would require regular booster vaccinations (perhaps as frequent as 3 months), which is not considered a long-term sustainable strategy

  • alternative vaccines, including variant-specific vaccines, may be available in 2022 and may be better suited to provide long-term protection against the Omicron variant or other newer variants

JCVI will continue its ongoing review of the booster program, in particular with respect to the timing and value of any second booster dose for the most vulnerable. This is an evolving situation. Additional rapid response measures may still be needed if there are substantial changes in our understanding of vaccine protection against the Omicron variant, or major changes in the ongoing epidemiology of COVID-19. In the meantime, the latest data is reassuring and gives confidence that the booster vaccination program has significantly boosted the population’s immunity against serious illnesses of COVID-19, including against the Omicron variant.