Monitoring the Effectiveness of SARS-CoV-2 Vaccines in British Columbia
In December 2020, mRNA vaccines (vaccines that teach our cells how to create an immune response, e.g., Pfizer, Moderna), followed by a vectored vaccine (a vaccine made from a modified version of another virus, e.g., AstraZeneca) in February 2021, were the first SARS-CoV-2 vaccines authorized for use in Canada.
The introduction of vaccination for COVID-19 was a game-changing moment in our pandemic, and equally important was the immediate launch of research to study the new vaccine technologies, and to monitor the effectiveness of SARS-CoV-2 vaccines in the real world and in real time.
Through one of the most critical COVID-19 projects we are funding, Dr Danuta Skowronski, Epidemiology Lead, Influenza & Emerging Respiratory Pathogens at the BC Centre for Disease Control (BCCDC), is leading this novel and real-time vaccine effectiveness research. Vaccine effectiveness (VE) looks at strength, durability, and interchangeability (protection offered when mixing vaccines), among other factors, and allows researchers and public health experts to learn about vaccines in real-world populations (this is different from efficacy, which is based on clinical trial data).
VE monitoring is critical in guiding vaccine policies and programs (e.g., target populations, intervals between doses, number of booster doses), and it is this monitoring that informs changes to vaccine programming and evidence-based decision-making, especially in relation to variations in pandemic waves and variants of concern (VOC).
Early work included reporting of the strength and duration of SARS-CoV-2 vaccine protection against infection, including emerging VOC and serious outcomes. This included:
- Single-dose effectiveness in healthcare workers and long-term care facility residents;
- Comparing mRNA vaccines versus AstraZeneca effectiveness in younger adults;
- The strength, durability, and interchangeability of two-dose VE including mixing different types of vaccines and extended intervals between doses.
Early findings demonstrated:
- The mRNA formulations gave higher protection against infection compared to AstraZeneca, but both provided excellent protection against severe outcomes.
- An AstraZeneca dose, plus a single dose of an mRNA vaccine in a mixed two-dose schedule, is as effective as two mRNA doses.
- Protection was better with a longer interval between first and second doses, and that the decision to extend the interval between first and second doses in BC not only brought first dose protection to more people more rapidly, but it also may have resulted in better responses to one’s second dose.
Recent findings are demonstrating that:
- Two-doses of vaccine provided protection against the Delta variant in both teens and adults.
- As we transitioned from Delta to Omicron, VE against infection decreased, but against hospitalization it remained comparable.
- With the rise of Omicron in December 2021, two-dose protection against severe outcomes was also well-maintained in adults.
- A third vaccine dose boosted protection from Omicron for adults, but less so than for Delta, and offered comparative protection against hospitalization.
- The incremental value of booster doses during times of low incidence (not in a ‘wave’) needs further study.
Perhaps you’ve learned about some of these findings in Dr Henry’s modelling updates, demonstrating why research like this is vital to the progression of the COVID-19 pandemic, to our understanding of vaccination, for decision-making around vaccine programming, and to care for our population as we experience differing waves or periods of high incidence versus low incidence.
Both early and recent findings, as well as continued findings as this work progresses, have been, and will continue to be, used to guide decisions for vaccination in BC. With the loosening of public health restrictions, and the transition to weighing one’s own personal risk and self-management (going at your own pace), vaccination will continue to be critical in our ability to protect ourselves and others from COVID-19.
For vaccination to continue to offer this protection, we have to understand how the evolution of SARS-CoV-2 impacts vaccines and how well they work—across all age groups, in all settings, and against new VOC. Ongoing monitoring of VE is critical to assess: potential waning of vaccine protection; impact of booster doses; protection in children; and with continued evolution of VOC, evaluating the strength, durability, and interchangeability of vaccines is an ongoing need for all target groups.
For this reason, we are partnering with the BC Ministry of Health, the BCCDC, and private donors to ensure this research can continue to provide critical evidence, for as long as our pandemic continues to impact BC, and the world. It is research like this that has been shaping our pandemic response in BC, and saving lives; and it is research like this that will ensure we keep everyone protected as we look ahead and learn to live with COVID-19 as safely as we can.
Vaccination remains our strongest tool in our toolkit, and we need to understand vaccine effectiveness in real-time and continue monitoring and providing evidence for decision-making. Findings from this research have already had substantial impacts on public policy provincially, nationally, and internationally. If you’d like to support this work, you can donate via our Emergency Response Fund.