Project #4:
The effectiveness of COVID-19 vaccines against clinical outcomes: a test negative case control study using OpenSAFELY

The effectiveness of COVID-19 vaccines against clinical outcomes: a test negative case control study using OpenSAFELY

Background

As soon as SARS-CoV2 was identified as the virus causing the ongoing COVID-19 pandemic, scientists and vaccine manufacturers worked rapidly to develop vaccines against it. Since late 2020, the UK has been rolling out a phased mass vaccination programme in the adult population, starting with people at greatest risk of severe infection. In clinical trials with volunteers, all three of the UK’s currently authorised vaccines were good at protecting recipients against infection but now that the vaccination programme is underway, it is important to look at how protective the vaccines are in the real world.

Aims of the study

• To determine the type-specific vaccine effectiveness of individual deployed COVID-19 vaccines in preventing laboratory-confirmed SARS-CoV2 infection in specified subgroups of the population.
• To determine the type-specific vaccine effectiveness of individual COVID-19 vaccines used to vaccinate the UK population in preventing hospitalisation due to COVID-19 related disease in specified subgroups of the population.

Methods

In this study we will evaluate how good each vaccine is at protecting people against infection with SARS-CoV2, and also at preventing serious outcomes of COVID-19 such as hospitalisation. We will use a test-negative case control design study to compare COVID-19 vaccination status in people with symptoms of COVID19 who have a positive SARS-CoV2 test (cases) with people who also have symptoms but who have a negative test (controls). Using this study design, we will also look at the vaccines’ effectiveness in particular subgroups, such as the elderly and people with poorly functioning immune systems, to see if the vaccines work less well in some groups.

We will estimate the vaccines’ effectiveness in preventing infection and serious outcomes at different time points after the first and second doses of the vaccine, and after a booster dose if this is recommended. Logistic regression will be used to determine adjusted type-specific vaccine effectiveness estimates and we will repeat analyses at intervals for up to 3 years after the start of the vaccine rollout to detect waning VE.

We will use a secure analytic platform, OpenSAFELY, to run analysis codes against approximately 24 million routinely collected electronic health records (EHRs) for adult patients who are registered at GP practices. This study will complement other studies using different data sources or study design, and will add to the body of knowledge to inform the government’s expert independent advisory body, the JCVI, when it make recommendations on future vaccination policy.