How common are side effects of COVID-19 vaccines in Hong Kong?

The most common concern expressed in populations with low vaccine uptake is safety. Sometimes this is voiced as a specific worry, such as the potential association of thrombosis post-vaccination. Often it is couched in general terms, for instance, the belief that the ‘vaccines have been rushed’.

Side effects of vaccination can be divided into those which happen shortly after the vaccination and resolve without any long term complications and those which either cause long term complications or occur later. Up to date, more than 1.3 billion doses of COVID-19 vaccines have been given worldwide. We now have a really good handle on the side effect data.

We recently surveyed 3,233 OT&P patients who had been vaccinated. Although the majority reported no or minimal side effects, a small but significant percentage of people reported more significant post-vaccine symptoms with 9.9% taking time off work.

Side effects were less common with Sinovac than BioNTech vaccine. 79.5% of patients taking Sinovac reported no side effects compared to 50.4% taking BioNTech. 4.8% of patients who took Sinovac ranked their side effects as between 6-10 on a severity scale (moderate to severe) in comparison to 8.4% who took BioNTech.

 Difference in Side Effects
Sinovac v BioNTech
1-10 scale, 10 is most severe
  Sinovac BioNTech
No side effects (0) 66 (79.5%) 1564 (50.4%)
Mild-Moderate side effects (1 - 5) 13 (15.6%) 1277 (41.2%)
Moderate-severe side effects (6 - 10) 4 (4.8%) 261 (8.4%)

From international studies, we have an increasing understanding of some very rare but serious potential side effects with some COVID-19 vaccines. The recent serious side effects potentially relating to the AstraZeneca and Johnson and Johnson vaccines is counterintuitively a good example of the safety data around vaccination. The rare condition in question typically affects around 5 people per million per year. It seems to affect around 10 per million after vaccination (mostly younger females). This compares to the risk of thrombosis with the contraceptive pill (200 per million) or COVID-19 (>1000 per million). It is of course appropriate that any side effects are fully evaluated and in this case it is likely that this class of vaccinations will be reserved for older patients.

Regardless, we are currently identifying complications which are occurring at a rate of 1/20th of that attributable to the oral contraceptive pill which is available as an over the counter medicine in Hong Kong. It is also important to realise that these vaccines are not given in Hong Kong and the AstraZeneca order was cancelled following publication of this safety data.

In our vaccine survey, there were no serious complications and only 2 out of 3,233 people indicated that the side effects would stop them from taking a further dose. At least in our population, it does not seem that side effects are a significant barrier to vaccination. The side effects are consistent with data published internationally. There is no reason to believe that vaccines in Hong Kong are any less safe and effective than they have been shown to be in the rest of the world.

The full survey results are available here.

Topics: COVID-19, Vaccinations

OT&P Healthcare

OT&P Healthcare

OT&P Healthcare is a Premium Private Healthcare Practice in Hong Kong. Our priority is to help individuals to enhance and optimise their health by providing easy access to a wide range of excellent practitioners and information, supported by management systems and technology that ensure quality of service and value. Our Mission is to provide pre-eminent private healthcare in Hong Kong. We aim to be the best in class fully integrated healthcare service, providing a circle of care for all our patients' needs.