Coronavirus disease (COVID-19)

Several studies report high effectiveness of COVID-19 vaccines against SARS-CoV-2 infection and severe disease, however an important knowledge gap is the vaccine effectiveness against transmission (VET). We present estimates of the VET to household and other close contacts in the Netherlands, from February to May 2021, using contact monitoring data. The secondary attack rate among household contacts was lower for fully vaccinated than unvaccinated index cases (11% vs 31%), with an adjusted VET of 71% (95% confidence interval: 63–77).

A breakthrough infection occurred in a fully Comirnaty (BNT162b2) vaccinated healthcare worker with high levels of neutralising antibodies with the SARS-CoV-2 B.1.351 (Beta) variant in February 2021. The infection was subsequently transmitted to their unvaccinated spouse. Sequencing revealed an identical virus in both spouses, with a match of all nine single nucleotide polymorphisms typical for B.1.351. To the best of our knowledge, no transmission of any variant of SARS-CoV-2 from a fully vaccinated person has been described before.

The non-pharmaceutical interventions implemented to slow the spread of SARS-CoV-2 have had consequences on the transmission of other respiratory viruses, most notably paediatric respiratory syncytial virus (RSV) and influenza. At the beginning of 2020, lockdown measures in the southern hemisphere led to a winter season with a marked reduction in both infections. Intermittent lockdowns in the northern hemisphere also appeared to interrupt transmission during winter 2020/21. However, a number of southern and northern hemisphere countries have now seen delayed RSV peaks. We examine the implications of these unpredictable disease dynamics for health service delivery in Europe, such as paediatric hospital and intensive care bed space planning, or palivizumab prophylaxis. We discuss the challenges for RSV vaccine trials and influenza immunisation campaigns, and highlight the considerable research opportunities that have arisen with the SARS-CoV-2 pandemic. We argue that the rapid advances in viral whole genome sequencing, phylogenetic analysis, and open data sharing during the pandemic are applicable to the ongoing surveillance of RSV and influenza. Lastly, we outline actions to prepare for forthcoming influenza seasons and for future implementation of RSV vaccines.

Evidence on COVID-19 vaccine efficacy/effectiveness (VE) in preventing asymptomatic SARS-CoV-2 infections is needed to guide public health recommendations for vaccinated people. We report interim results of a living systematic review. We identified a total of 30 studies that investigated VE against symptomatic and/or asymptomatic infection. In fully vaccinated individuals, VE against symptomatic and asymptomatic infections was 80–90% in nearly all studies. Fully vaccinated persons are less likely to become infected and contribute to transmission.

We analysed 9,030 variant-specific RT-PCR tests performed on SARS-CoV-2-positive samples collected in France between 31 May and 21 June 2021. This analysis revealed rapid growth of the Delta variant in three of the 13 metropolitan French regions and estimated a +79% (95% confidence interval: 52–110%) transmission advantage compared with the Alpha variant. The next weeks will prove decisive and the magnitude of the estimated transmission advantages of the Delta variant could represent a major challenge for public health authorities.

We investigated a COVID-19 outbreak of the SARS-CoV-2 Delta variant of concern in a London care home, where 8/21 residents and 14/21 staff had received a single dose of Vaxzevria (ChAdOx1-S; AstraZeneca) vaccine. We identified 24 SARS-CoV-2 infections (16 residents, 8 staff) among 40 individuals (19 residents, 21 staff); four (3 residents, 1 staff) were hospitalised, and none died. The attack rate after one vaccine dose was 35.7% (5/14) for staff and 81.3% (13/16) for residents.

We compared the performance of SARS-CoV-2 neutralising antibody testing between 12 European laboratories involved in convalescent plasma trials. Raw titres differed almost 100-fold differences between laboratories when blind-testing 15 plasma samples. Calibration of titres in relation to the reference reagent and standard curve obtained by testing a dilution series reduced the inter-laboratory variability ca 10-fold. The harmonisation of neutralising antibody quantification is a vital step towards determining the protective and therapeutic levels of neutralising antibodies.

SARS-CoV-2 Delta (B.1.617.2) variant of concern (VOC) and other VOCs are spreading in Europe. Micro-neutralisation assays with sera obtained after Comirnaty (BNT162b2, BioNTech/Pfizer) vaccination in 36 healthcare workers (31 female) demonstrated significant fold change reduction in neutralising titres compared with the original virus: Gamma (P.1) 2.3, Beta (B.1.351) 10.4, Delta 2.1 and 2.6. The reduction of the Alpha (B.1.1.7) variant was not significant. Despite being lower, remaining neutralisation capacity conferred by Comirnaty against Delta and other VOCs is probably protective.

Residents in long-term care facilities (LTCF) experienced a large morbidity and mortality during the COVID-19 pandemic in Spain and were prioritised for early COVID-19 vaccination. We used the screening method and population-based data sources to obtain estimates of mRNA COVID-19 vaccine effectiveness for elderly LTCF residents. The estimates were 71% (95% CI: 56–82%), 88% (95% CI: 75–95%), and 97% (95% CI: 92-99%), against SARS-CoV-2 infections (symptomatic and asymptomatic), and COVID-19 hospitalisations and deaths, respectively.