Public health control measures for COVID-19

Public health authorities can take several measures to mitigate the negative effects of COVID-19 at individual and community or population level.

Key public health measures and their main aims are:

• Vaccination to reduce the risk of severe COVID-19 disease.
• Surveillance (including sequencing) to obtain an overview of the epidemiological situation and circulating variants, as well as identify new variants of potential concern [4].
• Non-pharmaceutical interventions to reduce the risk of SARS-CoV-2 transmission.

Vaccination

The single most effective measure to reduce the risk of severe COVID-19 disease is vaccination. Reducing severe COVID-19 disease prevents not only deaths but also reduces hospital admissions, which subsequently decreases the burden on healthcare personnel, supplies, and facilities, and reduces the impact of COVID-19 on other diseases.

As of March 2023, the COVID-19 vaccines authorised for use in the EU include:

• Comirnaty Original; Comirnaty bivalent Original/Omicron BA.1 and Comirnaty bivalent Original/Omicron BA.4-5 (BioNTech and Pfizer);
• Spikevax Original; Spikevax bivalent Original/Omicron BA.1 and Spikevax bivalent Original/Omicron BA.4-5 (Moderna);

• Valneva;
• Nuvaxovid (Novavax);
• Vaxzevria (AstraZeneca);
• Jcovden (Janssen); and
• VidPrevtyn Beta (Sanofi Pasteur)[42].

The evidence base is continuously evolving with ongoing studies, including studies with adapted vaccines and newly emerging virus variants. Clinicians and public health practitioners should consult updates provided by regulatory and public health authorities on a regular basis and follow local vaccination strategies [43,44].

Several institutions and initiatives monitor vaccine effectiveness and/or maintain living systematic reviews summarising the evidence of the vaccine effectiveness of COVID-19 vaccines and the duration of protection following vaccination [43,45,46].

Vaccine effectiveness

Vaccines reduce the risk of becoming severely ill with COVID-19. Despite varying vaccine effectiveness (VE) depending on the circulating variant and a gradual decrease in effectiveness observed in studies with a follow-up period of three to six months after the first booster dose, vaccines continue to be protective against severe COVID-19 and hospitalisations [47].

Studies have shown that COVID-19 vaccines provide some short-lived reduction in the risk of transmission of SARS-CoV-2 from one person to another due to a shorter infectious period and lower virus titres in vaccinated people [48]. However, COVID-19 vaccines do not stop transmission entirely. Vaccinated individuals can therefore still become infected and transmit the virus to others.

Vaccine safety

The EU/EEA-authorised COVID-19 vaccines all showed a very good safety profile in clinical trials before receiving recommendations for approval from the European Medicines Agency EMA.

Experience since licensing show that most vaccine side effects are transient and mild, and severe adverse events are extremely rare [49,50]. The Pharmacovigilance Risk Assessment Committee (PRAC) of EMA has reviewed several safety events and adapted product information accordingly [50]). One example is the update of the Summary of Product Characteristics following reports of myocarditis and pericarditis in association with COVID-19 mRNA vaccines in 2021.

The overall benefits of authorised COVID-19 vaccines in preventing COVID-19 outweigh the risks of side effects [49,50].

Duration of immunity

The best current predictor of protective immunity in previously infected or vaccinated individuals is the presence of SARS-CoV-2 neutralising antibodies in serum. As time elapses following vaccination, protection against infection wanes as serum antibody titres gradually decline. However, it can be restored by administering booster vaccine doses.

Natural infections induce antibody levels that are lower when compared to vaccination. However prior SARS-CoV-2 infection reduces the risk of SARS-CoV-2 reinfection [51,52].

As COVID-19 continues to evolve, more individuals globally are acquiring what is known as ‘hybrid immunity’ (immunity conferred by a combination of vaccination and at least one prior infection). Individuals with hybrid immunity show the highest level and duration of protection against re-infection, hospital admission, and severe disease [52].

Non-pharmaceutical interventions

Individuals, communities, and institutions can apply non-pharmaceutical interventions (NPIs) to further reduce the impact of SARS-CoV-2.

NPIs primarily aim to slow the spread of the virus through infection protection and physical distancing measures:

• Individual NPIs include standard hygiene precautions such as hand-washing and respiratory etiquette, as well as avoiding contact and staying at home when feeling unwell or experiencing respiratory symptoms.
• Community NPIs are recommendations or mandates for testing, isolation and quarantine, mask use in public spaces and transport for source control and personal protection, social distancing measures to limit mass gatherings and congregations, as well as temporary closures and stay-at-home orders.

The use of medical face masks for source control and personal protection can be indicated, particularly during periods of high community transmission and where physical distancing is difficult or impossible.

Decisions on when to implement non-pharmaceutical public health and social measures, in addition to offering vaccination, depend on the epidemiological and healthcare situation, and require a balanced assessment of risks and benefits including their potential mid- and long-term socio-economic impact, as well as appropriate risk communication and community engagement [53].