Preliminary public health considerations for COVID-19 vaccination strategies in the second half of 2022

Key messages

• In the current post-acute phase of the pandemic, the introduction and emergence of new SARS-CoV-2 variants with increased transmissibility and/or immune escape capacity, together with waning protection against infection and severe disease from natural or vaccine-induced immunity, can result in new waves of virus transmission and surges of COVID-19 cases with a subsequent rise in hospitalisations, ICU admissions and deaths.
• As of 10 July 2022, the overall notification rates of COVID-19 cases in the EU/EEA remain high and have been increasing for the past five weeks. Case rates among people aged 65 years and over increased in 23 of the 27 reporting countries. These increases are still relatively recent, and they signal the start of a widespread wave driven by the BA.4 and BA.5 variants of concern.
• As of 3 July 2022, based on GISAID or the European Surveillance System (TESSy) data, Omicron BA.4 or BA.5 are the dominant circulating SARS-CoV-2 variants (>50%) in 18 EU/EEA countries, and, based on projections, the proportion of all COVID-19 cases due to infection with BA.4 or BA.5 will exceed 95% in most EU/EEA countries by end-July 2022.
• The increasing transmission among older age groups is starting to translate into severe disease, and, as of 10 July 2022, 12 countries reported an increasing trend in either hospital or ICU admissions/occupancy compared with the previous week. At the same time, even though the EU/EEA death rate has remained stable for the last five weeks, the forecast for the period up to 31 July indicates that both case notification rates and death rates will increase.
• As of 10 July 2022, the cumulative uptake of the primary COVID-19 vaccination course in the total population in the EU/EEA reached 72.8%, and 52.9% for the first booster dose. Among individuals aged 60 years and older, vaccine uptake is higher, 90.8% and 83.1% for the primary course and the first booster respectively, but still with significant disparities across EU/EEA countries.
• Currently, 20 countries recommend the administration of a second booster dose, mostly for age groups from 60+ to 80+ years and for long-term care facility (LTCF) residents, with a time interval after the first booster dose varying between three to five months. Approximately 16.5 million second booster doses have been administered so far (data reported to TESSy by 21 countries), the majority among those 60+ (88%), and with a median uptake of 11.6% among 60+ (range: <0.1-59.5%) and 20% among 80+ (range: 0.1-80.1%).
• Published literature indicates that vaccine effectiveness (VE) against severe outcomes caused by Omicron remains high, including among older age groups, with continued strong protection generally around 80−90% around two to three months after receiving the first booster, albeit with the balance of evidence indicating gradual waning after three to six months (VE estimates in the range 53-100%). A second mRNA booster dose restores VE against severe disease, which remains stable for up to 10 weeks, but longer follow-up times are not yet available. Only limited data are available on VE against Omicron sub-lineages BA.4 and BA.5. A preliminary analysis from Portugal suggests that the VE may be reduced against infection with BA.5 as compared to infection with BA.2, while data from South Africa indicate that high VE against severe disease has been maintained during the BA.4/BA.5 dominant period.
• The analysis of severe outcomes of disease among COVID-19 cases having received a first booster dose (TESSy data) shows that hospitalisation and death are rare in this group (0.6% and 0.1% respectively); nevertheless, the adjusted risk of hospitalisation and death is higher in those who received the first booster dose more than three months previously, older age groups (80+ and 60 to 79) and males.
• Mathematical modelling shows that for countries with an uptake of >40% for the first booster in the whole population, a second booster rollout among 60+ can have a substantial impact on restoring vaccine-induced protection against hospitalisation in this population from mid-July to the end of 2022, with an expected median absolute increase of 17% (95% UI 6-34%) on 1 November 2022. For countries with an uptake of <40% for the first booster in the whole population, closing the vaccination coverage gaps of the primary series and the first booster has a larger overall effect than a second booster rollout, with an expected median absolute increase of population-level vaccine-induced protection against hospitalisation of 16% (95% UI 10-41%) and 5% (95% UI 1-24%) on 1 November 2022, respectively. Furthermore, an earlier second booster rollout among 60+ in mid-July 2022 results in a larger vaccine-induced protection against hospitalisation for the rest of 2022 compared to a later second booster rollout. The benefit in terms of vaccine-induced protection against hospitalisation in the population 60+ decreases the more the starting date of the second booster rollout is moved later (we evaluate a starting date in July, August, September, or October).

Public health considerations

Considering the above, the following public health considerations provide some guidance for vaccination strategies and the use of additional booster doses of mRNA vaccines in the second half of 2022:

• At this stage of the pandemic, the objective of COVID-19 vaccination campaigns continues to be to reduce COVID-19 hospitalisation, severe disease and death, and to protect health systems.
• Improving vaccine uptake of the primary course and first booster dose in eligible individuals who are yet to receive them remains a priority, especially for population groups at higher risk of severe outcomes and for countries with lower uptake of primary course and first booster dose.
• An early second booster rollout, not only among 80+, but also for adults between the ages of 60 and 79 years and individuals with underlying comorbidities regardless of age, should now be considered to prevent severe disease and safeguard health system capacity, and countries should consider a rapid deployment. This would be particularly relevant and impactful in countries where the BA.4/BA.5 wave is starting or has not yet peaked. Second boosters could be administered at least four months after the previous one, with a focus on people who received a previous booster more than six months ago.
• At the moment, for immunocompetent individuals below 60 years of age, unless they have underlying comorbidities, there is no clear epidemiological evidence to support the administration of a second booster.
• The early administration of a second booster dose with currently available vaccines to healthcare workers (HCW) and personnel working in LTCFs for infection control purpose, is likely to offer only modest benefits in terms of limiting the risks of transmission to vulnerable people in their care, and be of limited duration. HCW and LTCF personnel may receive a second booster for their own protection if they belong to any prioritised population group based on age or underlying comorbidities. It should be ensured that LTCF residents receive the recommended booster doses; non-pharmaceutical interventions (NPIs) in healthcare settings including LTCFs remain effective measures to protect vulnerable individuals; and access to therapeutics is an additional key measure for the protection of LTCF residents from severe outcomes.
• In addition, in anticipation of further waves of infection that may arrive in the autumn/winter season, countries should consider the need for rollout of further additional booster doses of mRNA vaccines for population groups at risk of severe disease (e.g. 60+,individuals with underlying comorbidities, immunocompromised individuals and pregnant women) later in the year, possibly combining campaigns for vaccination against COVID-19 and influenza, taking into account any new evidence available at that time on the benefit/risk profile of repeated boosters and the impact on the capacity of health systems to deliver vaccinations in the context of other competing public health priorities in the post-pandemic phase.
• The boosting of HCW and LTCF personnel should also be considered for this later rollout. If adapted, vaccines will show increased neutralisation against Omicron variants, indicating a possible higher effect against infection and transmission, they may be used to provide both direct and indirect protection.
• The need for, and optimal timing of further additional booster doses in autumn/winter may vary across countries, especially depending on the timing of rollout of second boosters in spring/summer 2022 and emerging evidence of continued protection against severe disease in those that have received a second booster dose.
• Updated Omicron-adapted vaccines will likely be authorised for use in the EU in September and possibly available sometime during the last trimester of 2022, however the distribution timeline and available supplies are currently being defined with manufacturers. Nevertheless, it is important to continue the efforts to increase vaccination rates with available vaccines for groups at high risk of severe disease in a timely manner, and not to wait for the new Omicron-adapted vaccines.
• Future vaccination strategies may also differ depending on the availability of the updated vaccines and their characteristics. Countries may have to use different types of vaccines for different strategies and population groups depending on the characteristics of the updated vaccines compared to first-generation ones and considering emergence of new variants.
• Communication initiatives to promote uptake of additional vaccine doses, and to promote completion of the primary series by those who have not yet done so face recurring and emerging challenges. These include complacency towards the threat of COVID-19, the need to provide evidence-based reassurances to address lower confidence in vaccine effectiveness and concerns about side effects, as well as potential confusion in the public as to how boosters will be offered in the coming months, timelines for adapted vaccines, who should receive these and when. This context stresses the importance of understanding and addressing individuals’ and communities’ beliefs, concerns and expectations regarding the vaccine and the disease. Clear information should be provided around the rationale for recommendations, and the benefits of the primary course and boosters for different population groups, including for those who already had the disease.

These public health considerations are based on current scientific evidence and epidemiological trends, and will be periodically reassessed. The scope of these considerations is focused on the second half of 2022, with an emphasis on the case for booster vaccination and closing the primary vaccination gap in the late summer/early autumn, and not for longer term COVID-19 vaccination strategies. National Immunisation Technical Advisory Groups (NITAGs) will ultimately make national decisions on the use of COVID-19 vaccines, taking into account the previous vaccination uptake and the epidemiological situation in their countries.