Side Effects of Hong Kong's COVID-19 Vaccines in 10 Easy Questions

Does everybody who takes a COVID-19 Vaccine get some side effects?

Answer: No, the majority of people get no side effects and those that happen are mostly mild.

In OT&P's survey of vaccination in 3,633 patients in Hong Kong, more than half of people who were vaccinated had no side effects. Side effects were less common with the Sinovac vaccine. Side effects were also more common with the second dose and in people who had previously had Covid. The vast majority of side effects were mild and settled within 24 - 48 hours. In the OT&P study, only 2 patients said that the side effects would stop them from having another dose. This data is compatible with numerous international studies on hundreds of millions of Covid vaccine doses.

What are the most common side effects of the BioNTech vaccine?

Answer: Injection site pain, fatigue, headache and muscle pains.

The most commonly reported side effects with the first dose are pain at the injection site which affects one-third of people. This is followed by fatigue (21%), headache (15%), muscle aches (11%) and joint pain (5%). In the vast majority of people, these side effects have disappeared within two days.

What are the most common side effects of the Sinovac vaccine?

Answer: Fatigue and injection site pain.

In a recent study, published in the Lancet, of more than 11 thousand volunteers given Sinovac, there were no serious side effects^[1]. Mild side effects occurred in the vaccination group (18.9%) compared to the placebo group (16.9%). Fatigue (8.2%) and injection site pain (2.4%) were the most commonly reported side effects. Almost 80% of people in the OT&P survey described no side effects with Sinovac. The most common complaint reported from international studies was injection site pain. Diarrhoea and muscle aches have also been described, but as with BioNTech in the vast majority of cases, these side effects have disappeared within two days.

Are side effects always a bad thing?

Answer: No, these mild side effects are a symptom of the body developing immunity.

Mild side effects, such as injection site pain or fatigue and muscle pain, are common in other vaccinations. They are a side effect of the immunological response to the vaccine. A battle occurs within the body in which nature triggers an immune response which is protective for the future. It has been well reported that mRNA vaccines have more mild side effects. They have also been shown to be more effective than more traditional killed vaccines (such as Sinovac).  A study from Hong Kong University published in The Lancet showed 10X higher antibody levels in patients given BioNTech in comparison to Sinovac^[2]. This has also been our findings with OT&P patients. We recently reviewed more than 800 post-vaccine antibody tests. We also saw significantly higher antibody levels after the BioNTech vaccination.

Does anaphylaxis (severe allergic reaction) happen with Covid vaccines?

Answer: Yes, but very rarely.

It is estimated that anaphylaxis occurs around five in every million doses of BioNTech vaccine. We do not yet have adequate data to assess the incidence of anaphylaxis with Sinovac, it is likely to be less common. The vast majority of these allergic reactions occur within 15 to 30 minutes of the injection. This is why we must wait in the immunisation hall after vaccination. Fortunately, anaphylaxis is easy to treat. If you have a history of anaphylaxis or severe allergic reaction you should discuss this with your doctor. The majority of people who have a history of allergy can take Covid vaccines without any problem.

Does Myocarditis or Pericarditis (Heart Inflammation) occur with Covid vaccines?

Answer: Yes, but very rarely.

There have recently been reports of Myocarditis and Pericarditis (Heart Inflammation) after the BioNTech vaccine. There is no evidence of association with Sinovac vaccine although we have significantly less safety data on Sinovac and it is not possible to exclude an association. Research is ongoing, current reports suggest an incidence of around 20 per million vaccines. These seem more likely to affect younger males after the second dose. The majority resolve within one week although some require hospitalisation. It seems reasonable to advise avoiding intense physical activity for a few days after Covid vaccination. It is also important to realise that myocarditis and pericarditis are relatively common after Covid and the risks associated with vaccination are many times less than the risks of the disease.

Do Covid vaccines increase the risk of heart disease or strokes?

Answer: No

There is an enormous amount of safety data for the BioNTech vaccine and there is no suggestion of an increase in heart attacks, strokes or thrombosis. There is no evidence of thrombotic risk with Sinovac but we have significantly less data. Covid significantly increases the risk of heart disease and strokes. It is even more important for individuals who have risk factors for thrombosis or blood clotting to be vaccinated.

Is Bell’s palsy (facial nerve weakness) more common after Covid vaccine?

Answer: Possibly but we need more data

It is sometimes hard to be certain when rare medical conditions occur in association with vaccination as to whether the vaccine is responsible. In an average year, Bell’s palsy typically occurs around 15 - 30 times in every 100,000 people. One study in Israel suggested no difference in the incidence of Bell’s palsy in vaccinated and non-vaccinated people. A recent review in the Lancet suggested that Bell’s Palsy after BioNTech vaccine may be 2 - 3 times more common^[3]. Again we do not have enough data to assess risk for Sinovac. It seems reasonable that people who have a history of Bell’s palsy should discuss the risk-benefit of vaccinations with their doctor.

Are side effects more common if I have diabetes or high blood pressure?

Answer: No

There is a common misconception in Hong Kong that vaccinations have more side-effects in people who have other medical conditions or take medication. This is not the case. People who are older, have diabetes, high blood pressure, obesity and some other medical conditions have an increased risk of death from Covid and it is even more important that they are vaccinated. There is no evidence for an increase in side-effects and there is no need to have a body check before being vaccinated. Anyone who is able to take a flu vaccination is perfectly able to take a Covid vaccination.

Are side effects more common in the elderly?

Answer: No in fact the opposite is the case

Again there is a misconception that Covid vaccinations have more side effects in the elderly. In fact the opposite is the case. The elderly have less aggressive immune response than the young so the battle within the body creates less side effects. The elderly are more vulnerable and are much more likely to die of Covid than the young. They are also less likely to have side effects.

Hong Kong has done incredibly well in controlling the size of the epidemic in our city. Unfortunately, the increasing transmissibility of the Delta variant means that it is impossible that we prevent infections in Hong Kong forever. Vaccination is the only reasonable long term solution. Covid vaccines are highly effective and safe in comparison to other vaccines which are used widely. In Hong Kong significantly less than 10% of the vulnerable elderly are vaccinated. This represents a huge risk to our city.

References

1. Tanriover MD; Doğanay HL; Akova M;Güner HR; Azap A; Akhan S; Köse Ş;Erdinç FŞ; Akalın EH;Tabak ÖF; Pullukçu H;Batum Ö; Şimşek Yavuz S; Turhan Ö; Yıldırmak MT; Köksal İ; Taşova Y; Korten V; Yılmaz G; Çelen MK; Altın S; Çelik İ; Bayındır Y; Karaoğlan İ; Yılmaz A; Özkul A; Gür H; (n.d.). Efficacy and safety of an inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac): interim results of a double-blind, randomised, placebo-controlled, phase 3 trial in Turkey. Lancet (London, England). https://pubmed.ncbi.nlm.nih.gov/34246358/.

2. Lim, W. W., Mak, L., Leung, G. M., Cowling, B. J., & Peiris, M. (2021, July 15). Comparative immunogenicity of mRNA and inactivated vaccines against COVID-19. https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(21)00177-4/fulltext.

3. Cirillo, N., & Doan, R. (2021, June 7). Bell's palsy and SARS-CoV-2 vaccines-an unfolding story. The Lancet. Infectious diseases. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8184125/.