Vaccination remains one of the best protective measures against COVID-19. Recommendations for vaccination are in place in all Member States and roll-out of vaccination is ongoing. The European Medicines Agency (EMA) and the European Centre for Disease Prevention and Control (ECDC) urge EU citizens to get vaccinated and to adhere to the recommended number of doses.1 This is particularly important taking into account the spread of the Delta variant of SARS-CoV-2 (the virus that causes COVID-19), the need to protect citizens, especially those at risk of severe COVID-19, and the desire to open up our societies and relax restrictions.
Current COVID-19 situation in the EU
The Delta variant (B.1.617.2) is a variant of concern that is spreading fast in Europe and may seriously hamper efforts to control the pandemic. Evidence suggests it is 40% to 60% more transmissible than the earlier Alpha (Β.1.1.7) variant which was the first major variant of concern in the EU. In addition, the Delta variant may be associated with higher risk of hospitalisation.
ECDC estimates that by the end of August the Delta variant will represent 90 percent of all SARS-CoV-2 viruses circulating in the EU. This makes it essential for countries to speed up vaccination programmes, including delivery of second doses where recommended, and to close the immunity gaps and opportunities for further emergence of variants, as soon as possible.
Importance of completing the recommended vaccination courses
Adherence to the recommended vaccination course,[1] in line with the product information, is vital to benefit from the highest level of protection against the virus. As the Delta variant increasingly spreads, the importance of completing the recommended courses is underlined. Preliminary evidence[2] suggests that both doses of a 2-dose COVID-19 vaccine like Comirnaty, Spikevax or Vaxzevria are needed to provide adequate protection against the Delta variant.
The risk of severe disease and mortality caused by COVID-19 is greater for older age groups and those with other underlying conditions, emphasising their need for completing the recommended vaccination courses. However, there are still 10 EU/EEA countries where nearly 30% or more of individuals older than 80 years have not yet completed the recommended vaccination course, according to ECDC’s Vaccine Tracker.
Similarly, to protect frail and elderly individuals in closed settings, such as hospitalised patients or residents in long-term care facilities, further work is needed in some countries to increase vaccine uptake among healthcare workers and staff of such institutions. EMA and ECDC encourage healthcare and care workers to take up offers of vaccination as soon as possible, to protect themselves, their families and those they work with and care for.
In order to respond to these needs and increase vaccination coverage, countries may adapt their strategies, for example regarding the interval between first and second dose, based on the epidemiological situation and circulation of variants, and the evolving evidence on vaccine effectiveness against variants.
Using a different vaccine for the second dose
Another such adaptation is that experts responsible for the vaccination programmes in over half of Member States have decided, with a view to their national situations, to use different vaccines for the second dose from the ones used for the first dose. For example, in some countries people may be offered a second dose of an mRNA vaccine such as Comirnaty or Spikevax after a first dose of the adenoviral vector vaccine, Vaxzevria.
A heterologous vaccination strategy (sometimes referred to as ‘mix and match’), in which a different vaccine is given for the second dose in a recommended 2-dose schedule, has historically been applied for some other vaccines.[3] There are good scientific grounds to expect this strategy to be safe and effective when applied to vaccination against COVID-19. The use of a heterologous vaccination strategy may allow populations to be protected more quickly and make better use of available vaccine supplies.
Currently, EMA and ECDC are not in a position to make any definitive recommendations on use of different COVID-19 vaccines for the two doses. Nonetheless, preliminary results from studies in Spain,[4] Germany[5],[6] and the UK[7] suggest a satisfactory immune response and no safety concerns. More data are awaited shortly, and EMA will continue to review these as they become available.
Will a booster dose be needed after completing the recommended vaccination course?
It is currently too early to confirm if and when a booster dose for COVID-19 vaccines will be needed, because there is not yet enough data from vaccination campaigns and ongoing studies to understand how long protection from the vaccines will last, also considering the spread of variants.
However, in case booster doses may become needed, EMA and ECDC are already collaborating with one another and the national immunisation technical advisory groups (NITAGs), who are national experts advising on vaccination programmes coordinated by ECDC. Any new evidence that becomes available on this topic will be rapidly reviewed. Real world effectiveness data from Europe and other parts of the world, are of particular interest to supplement data from clinical trials investigating booster doses.
EMA is also engaging with vaccine developers to coordinate submission of these data. This should ensure that the regulatory steps to enable the possibility of using a booster dose can be undertaken as soon as possible should it prove necessary.
Other protective measures
Other measures such as mask wearing and social distancing will need to be maintained at a level sufficient to contain community transmission of the Delta variant until more of the populations are fully vaccinated, in order to avoid a resurgence of cases with a possible increase in hospitalisations and deaths. Citizens should follow national advice to protect themselves and others.
Working together for public health
Advice on how vaccinations should be given remains the prerogative of the NITAGs guiding the vaccination campaigns in each Member State. These bodies are best placed to take into account the local conditions, including the spread of the virus (especially any variants of concern), the availability of vaccines, and the capacities of the national health system.
EMA and ECDC re-emphasise the need to ensure that as many people as possible are fully vaccinated against COVID-19. We will continue to work closely together with other EU bodies and national agencies, to share the best scientific data and help Member States come to the optimal decisions to protect public health in the light of their national situations.
We remain fiercely committed to following the scientific evidence and communicating transparently our recommendations and decisions. More information is available from our websites at https://www.ecdc.europa.eu/en/
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