Sinovac Vaccine Side Effects: Stroke-Like Symptoms Plus 11 Others

What are Sinovac vaccine side effects? I enumerate 11 of them in this article noting my own experience after being inoculated with Sinovac vaccine. Read on to find out.

I would not have written this article had I not read an article about Sinovac vaccine side effects and videos about its efficacy in Malaysia and Thailand. I also listened to Sinovac Chief Executive Officer’s interview about the vaccine’s efficacy in general and the challenges encountered during its development.

Although I have not experienced any notable symptoms since the administration of my first dose last May 17, and the second dose last June 17, I did experience cramps and numbness at night 19 days after the second dose. But it lasted only two days as I resumed my jogging routine last Wednesday, after an almost two-month hiatus.

Is Stroke a Possible Sinovac Vaccine Side Effect?

According to Reuters, government-appointed experts in Thailand reported six unusual “stroke-like” side effects among Sinovac vaccine recipients. Six medical personnel experienced stroke-like symptoms, including numbness in their limbs.

I immediately thought of my experience after two weeks of getting inoculated with the Sinovac vaccine. While I have not experienced virtually anything unusual after the first and second dose of Sinovac, I did have numbness in my extremities and foot cramps after the two-week post-second dose period. I thought I did have a stroke and hurriedly took my blood pressure when that happened during the middle of my sleep at around 2 am.

I got a blood pressure reading of 99/58 with a heartbeat of 50. I tried again, 98/60 with a heartbeat of 51. You might think I have bradycardia, or an abnormally slow heartbeat, but I am a strong runner. So my doctor says I’m okay with that blood pressure.

But then my foot and legs felt numb, and I felt my right foot will have cramps. If I point my foot downwards, I’m pretty sure I will get foot cramps. A little bit alarmed, I quickly pulled my toes upwards to stretch the muscle, to prevent cramps from happening — with success. I shook and massaged my hands and legs to regain blood circulation. It worked.

Having leg and foot cramps like this happened to me for the first time in years. And I could not remember anything that may be a contributory factor to this condition. Is it because of the Sinovac vaccine?

The cause of cramps is considered idiopathic, meaning, the exact cause is unknown. My experience may be unrelated to the vaccine. I am not so sure.

So what are Sinovac vaccine side effects that we need to be aware of? I was curious, too so I searched the literature.

Scientific Basis of the List of Sinovac Vaccine Side Effects

Aside from my personal experience which may not even be linked to the vaccine, the next section lists the side effects reported since its administration. This list is based on a meta-analysis conducted by Pormohammad et al. (2021).

A meta-analysis reviews a number of independent studies of the same subject, in order to determine overall trends. I arranged the side effects of inactivated COVID-19 virus where the Sinovac vaccine belongs according to the most frequently reported symptoms.

But I would like to note that in reading the paper, the side effects of inactivated virus vaccines like Sinovac are relatively fewer compared to the other type of vaccines. At the same time, the same study reported that the efficacy of Inactivated COVID-19 Vaccines against spike protein (S-protein) found in COVID-19 SARS COV2 is 94.1%, two weeks after the second dose.

That’s quite high. You are protected from sure death or being hospitalized for severe infection. But we must be watchful of the COVID-19 variants. Booster shots of the Sinovac vaccine may be needed to keep its efficacy up.

We should not let our guards down as the virus mutates fast. As of this writing, Indonesia is struggling with the delta variant of COVID-19, where children significantly comprised the victims. Looking at the graph of infections, they are having another spike (Fig. 1.)

Sinovac vaccine side effects
Figure 1. Spike of new COVID cases in Indonesia on July 10, 2021.
Indonesia’s COVID-19 outbreak attributed to the COVID-19 delta variant.

While you may have read terms on the side effects of vaccines, I expound on them further so you can easily discern what doctors mean by the terminologies that they tell their patients. Many doctors or medical professionals forget that they are talking to laypeople, not colleagues.

Thus, I clearly describe each one for easy understanding.

This site’s purpose is to simplify terms and concepts. Here are Sinovac vaccine side effects found in the literature with notes on my experience.

11 Sinovac Vaccine Side Effects

Here are COVID-19 inactivated virus side effects (includes Sinovac vaccine side effects) listed by Pormohammad et al. (2021).

Injection-Site Pain

I never experienced injection-site pain. Maybe the nurse who injected me in those two doses is quite good at not hitting a nerve in the deltoid muscle. I thought the nurse inoculated me with distilled water. No pain at all.

Introducing a foreign body as that dose of vaccine with the inactivated virus among other substances to preserve the vaccine and make it efficient, plus the low liquid temperature can make your body react immediately. Experts say it should be gone in one to two days.

In my case, however, there’s not even pain to deal with.


According to Hopkins Medicine, myalgia refers to muscle aches and pain. The pain can involve ligaments, tendons and fascia, the soft tissues that connect muscles, bones and organs.

I experienced none.


Johns Hopkins Medicine defines arthralgia as pain in one or more of your joints. The pain may be described as sharp, dull, stabbing, burning or throbbing, and may range in intensity from mild to severe.

Again, I experienced nothing of the sort.


The National Institute of Diabetes and Digestive and Kidney Diseases defines diarrhea as loose, watery stools three or more times a day. Accordingly, diarrhea may be acute, persistent, or chronic.

Acute diarrhea means severe and sudden in onset and typically lasts one to two days. Persistent diarrhea lasts from two to four weeks, while chronic diarrhea lasts at least four weeks.

Nada. I did not experience diarrhea at all.


Fatigue is extreme tiredness. Again, I experienced none because I started to jog around right after my second dose of the Sinovac vaccine.


Swelling on the arm where I got the injection? None.


Vomiting? None at all in my case.


I had a little itchiness on my scalp. But it went away after I took a bath. A little bit itchy but nothing to be alarmed about.


During the first week of the first dose, I felt a little bit warmer than usual. My lower body appears to be warmer than before for some reason. But it’s never a fever.

You have a fever if your body temperature rises above the normal range of 98–100°F (36–37°C). It is a common sign of an infection. As a person’s body temperature increases, you may chill, feeling cold until the temperature levels off and stops rising.

Within that span between the doses and after the doses until now, nothing. I had no fever.


Headache is pain that may occur on one or both sides of the head or other parts of the head and radiate across the head from one point. It may be a sharp pain or a throbbing sensation.

I felt a little bit of headache but it’s nothing unusual as I sometimes have a headache if I focus on the computer’s screen for a long time. Nothing dramatic here.


Induration is a new word for me. This medical term means a localized hardening of soft tissue of the body. The area becomes firm, but not as hard as bone. Again, I had no such symptom.

The last of the Sinovac vaccine side effects, perhaps, would be the stroke-like effects which I have experienced. But there’s no scientific literature to support it, only anecdotal evidence in the recent news. It takes time for scientists to obtain data and make a definite statement about this phenomenon.

I do hope the creeping numbness of extremities doesn’t happen to you if you decide to have yourself vaccinated with Sinovac.

What Makes Sinovac Vaccine Different from the Other Vaccines?

Historically, vaccines protect a majority of people. It is a technology that we should be thankful for despite its imperfections. Now, six types of vaccines exist.

The development of the Sinovac vaccine uses the traditional method of vaccine development where the virus is inactivated. Inactivated vaccines contain viruses whose genetic material has been destroyed by heat, chemicals or radiation. The virus cannot infect human cells and reproduce themselves. They can, however, still trigger an immune response (GAVI).

To Vaccinate or Not to Vaccinate with Sinovac Given the Side Effects?

This question is difficult to answer as COVID-19 vaccines need to be evaluated for a long time to establish their effectiveness in the general population. People react differently to foreign substances in their bodies. You will never know the Sinovac vaccine side effects unless you have yourself inoculated.

You may experience the same numbness I had after more than two weeks of taking the second dose of the vaccine. It’s non-lethal anyway. It just went away. You will be rattled if the symptoms progress to the more debilitating Guillain-Barré Syndrome.

But one thing is for sure, with risk comes benefits. The higher the risk, the higher the benefits. No risk, no benefits.

For me, I’d take the risk of having those side effects as long as the benefit is not risking my life if I have a chance to do something about it.

I’d rather endure the side effects of a vaccine than suffer the severe impact of COVID-19 on my health. It may not only be the severe effects but my very life.

There may be some challenges in vaccine development, but giving yourself a layer of protection from an unknown threat is a better option than nothing at all.

While I started with hesitancy because of the likely Sinovac vaccine side effects, given my experience, I would say I have made a good decision. A good deal of my worries of getting infected by COVID-19 is gone.

But I still have to wear a mask as added protection in case a rogue virus comes to town.


Pormohammad, A., Zarei, M., Ghorbani, S., Mohammadi, M., Razizadeh, M. H., Turner, D. L., & Turner, R. J. (2021). Efficacy and Safety of COVID-19 Vaccines: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Vaccines, 9(5), 467.

© P. A. Regoniel 11 July 2021



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