First case study: Israel
Israel started its vaccination programme on 19 December 2020. As of 20 May 2021, almost 60% of its population has received two vaccine doses (see Figure 1). Israel largely used the Pfizer / BioNTech vaccine, an RNA-based vaccine requiring 21 days between the first and the second dose. Israel’s latest exit strategy included three different phases:
- 7 February 2021: measures included reopening of open-air nature reserves and parks. 25% of the population was fully vaccinated at that point (40% received at least one dose);
- 21 February 2021: ‘green passes’ (a form of COVID-19 certification status) were implemented to access venues such as gyms and concerts. 35% of the population was fully vaccinated at that point (50 % received at least one dose);
- 7 March 2021: more restrictions were lifted, including on gatherings of up to 20 people indoors and 50 outdoors. 44% of the population was fully vaccinated at that point (57% received at least one dose).
Many considered Israel’s mass-vaccination campaign a success story that could be a model strategy for other countries. Its slow exit strategy (which still uses some NPIs, such as the use of masks in indoor public spaces) combined with the high effectiveness of the Pfizer/BioNTech vaccine in preventing infections after a single dose, ensured a significant and constant reduction of daily new cases (see Figure 2). There are currently around 3 new cases per day per 1,000,000.
Israel national surveillance data were published on The Lancet on 5 May 2021. The effectiveness of two doses of the Pfizer/ BioNTech vaccine against SARS-CoV-2 infection was estimated to be over 90% (95·3% for symptomatic infection and 91·5% for asymptomatic infection). A recent pre-print (not peer reviewed) analysing vaccination and infection data in Israel also suggests that high vaccine uptake in adults is highly correlated with indirect protection of unimmunised children under 16.
Second case study: Chile
Chile started its vaccination programme on 24 December 2020. As of 20 May 2021, almost 50% of its population has received two vaccine doses (see Figure 1). Chile employed two different vaccines. 93% of the population received the CoronaVac vaccine (an inactivated vaccine produced by the Chinese company Sinovac) and the remaining 7 % received the Pfizer/BioNTech vaccine.
Despite the fast vaccination rollout, Chile faced another wave of COVID-19 cases and on 1 April 2021 announced tighter restrictions, including border closures. There were 363 daily new cases per 1,000,000 (see Figure 2). Only 20% of the population was fully vaccinated at that point (see Figure 1) and over 35% received at least one dose.
This spike in cases in Chile appears to have been a result of:
What has been discussed by the Scientific Advisory Group for Emergencies (SAGE) about the vaccination rollout and the lifting of restrictions?
The success of the COVID-19 vaccination campaign is the first criterion considered in the Government’s COVID-19 Response – Spring 2021 (the Roadmap) to allow the gradual lifting of restrictions. The Scientific Advisory Group for Emergencies (SAGE) has discussed in several meetings the relationship between vaccination rollout, the lifting of NPIs and an increase in transmission:
- During its 79th meeting on 4 February 2021, SAGE highlighted how, even with a high proportion of the population being vaccinated, lifting NPIs too quickly would lead to an increase in cases. SAGE discussed the advantages of lifting NPIs later, such as allowing continued reduction of cases and more people to be vaccinated. Modelling data commissioned by Scientific Pandemic Influenza Group on Modelling (SPI-M) supported these conclusions.
- During its 80th meeting on 11 February 2021, SAGE considered a brief on behavioural and social considerations when reducing restrictions produced by the Independent Scientific Pandemic Insights Group on Behaviours (SPI-B). SAGE concluded that it is essential to provide clear messages to people, especially highlighting why it is important to still adhere to certain protective behaviours, as their perception of risk would change as the vaccination campaign progresses.
- During its 83rd meeting on 11 March 2021, SAGE considered a SPI-B (Scientific Pandemic Insights Group on Behaviours) brief on ‘Behavioural considerations for vaccine uptake in Phase 2 and beyond’, that analysed adherence to NPIs following vaccination. SPI-B concluded that adherence to NPIs did not significantly change following vaccination, although some groups (such as people aged 16-29 years) were less likely to comply.
- During its 86th meeting on 8 April 2021, SAGE discussed a paper produced by SPI-M (Scientific Pandemic Influenza Group on Modelling) contributors on ‘Ready reckoners under vaccination’. These describe the relationship between different parameters, such as the reproduction number R, the number of contacts made outside home and school, vaccination rollout, and school opening. The analysis highlighted that a greater impact on transmission is expected following vaccination of younger age groups, given that on average they have a higher number of contacts than the older population. SAGE concluded that ‘these ready reckoners will be useful when considering the impact of relaxation of social distancing’.
- During its 88th meeting on 5 May 2021, SAGE discussed a paper produced by the Scientific Pandemic Influenza Group on Modelling, Operational sub-group (SPI-M-O) entitled ‘Summary of further modelling of easing restrictions – Roadmap Step 3’. SAGE concluded that it is “highly likely that there will be a further resurgence in hospitalisations and deaths at some point”, but that this resurgence will be smaller if measures to reduce contact between people continue and if the vaccine is rolled out to younger adults. Moreover it highlighted that, without any interventions, a new variant that is either more transmissible or able to escape the vaccine-triggered immune response could lead to a larger wave than that observed in January 2021. This could have implications with regards to the B.1.617.2 variant (first identified in India) (see POST Rapid Response COVID-19 vaccines: effectiveness against the B.1.617.2 variant and latest updates from trials).
Acknowledgements
POST would like to thank Professor Adam Finn (University of Bristol; Bristol Royal Hospital for Children) who acted as external peer reviewer in preparation of this article.
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