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Safety, side effects of Taiwan's Medigen COVID vaccine

Information on MVC COVID-19 jab as 600,000 inoculations begin Monday

Health worker holding dose of Medigen vaccine.

Health worker holding dose of Medigen vaccine. (CNA photo)

TAIPEI (Taiwan News) — As the nearly 600,000 doses of the domestic COVID-19 vaccine developed by Medigen Vaccine Biologics Corp. (高端疫苗, MVC) begin being distributed on Monday (Aug. 23), the Centers for Disease Control has provided a list of safety information about the jab.

Medigen is the first Taiwanese-developed vaccine for COVID-19, of which 614,204 doses have been tested and are ready for the first round of administration from Aug. 23-29. This initial round of Medigen shots will include people over the age of 65, those between the ages of 20 and 64 from the ninth category of eligible recipients, and members of the general public between 36 and 64.

Vaccination dose and interval

Currently, the Medigen vaccine is approved for those aged 20 and over. The dosage for one shot is set at 0.5 milliliters, and the vaccine is delivered in two doses with an interval of 28 days.

Safety and protective effect

The vaccine does not contain reproducible SARS-CoV-2 virus particles, and people will not acquire COVID-19 as a result of inoculation. Based on clinical trial results, the vaccine has been deemed to have a "good level of safety."

According to the analysis of its clinical trial results, data on the immunogenicity and serum neutralizing antibodies of Medigen recipients meet the standards based on protection-related indicators produced by vaccines obtained from abroad and approved for emergency use authorization (EUA).

In Phase II clinical trials, a subgroup of vaccine recipients who were tested for EUA purposes were found to have a seroresponse rate (potency of response) of 95.5%, far higher than the standard requirement of 50%.

Vaccination contraindications

Those who have a history of severe allergic reactions to vaccine components should not receive the vaccine.

Vaccine precautions

  1. Those who have a fever or are suffering from an acute moderate or severe disease should wait until their condition is stable before vaccination.
  2. Vaccines cannot be used interchangeably with other brands. If two doses of different COVID-19 vaccines are accidentally used, an additional shot is not recommended.
  3. The vaccine cannot be delivered too soon before or after another vaccine. An interval of at least 14 days is recommended between the COVID-19 vaccine and vaccines for other diseases.
  4. People with weakened immune function, including those receiving immunosuppressive therapy, may have a weakened immune response to the vaccine.

Pregnant and breastfeeding women

  1. At present, there is a lack of clinical trial and safety data for pregnant women, but clinical observational studies have shown that pregnant women infected with SARS-CoV-2 virus may be more likely to become severely ill than others. If pregnant women are at high risk of occupational exposure to COVID-19 or have chronic diseases likely to cause severe illness, they can discuss the benefits and risks of vaccination with their doctors first.
  2. If a breastfeeding woman is in a high-risk group (such as medical staff) recommended for inoculation, the vaccination should be completed. At present, the safety of the vaccine for breastfeeding women and the impact on breast milk or nursing infants has not been fully evaluated, but it is generally believed that it will not pose a risk. After being vaccinated, breastfeeding can continue.

Precautions after vaccination

  1. As a precaution for the low possibility that an allergic reaction may occur, recipients should remain at the site where the vaccine was administered for 15 minutes. After leaving, recipients are advised to observe themselves for symptoms for an additional 15 minutes.
    People who have had an acute allergic reaction to the injection should still stay at or near the vaccination site for at least 30 minutes after vaccination.
  2. Those who use antiplatelet or anticoagulant drugs or have abnormal blood coagulation function should apply pressure at the injection site for at least two minutes after the injection and observe whether there is still bleeding or hematoma.

Possible reactions and countermeasures after vaccination

  1. The most commonly reported reactions after the Medigen vaccination are pain, redness, and swelling at the injection site. One should avoid rubbing or scratching the injection site and instead apply ice.
  2. If one experiences an abscess, persistent fever, or severe allergic reaction (such as shortness of breath, wheezing, dizziness, rapid heartbeat, or body rash) and other symptoms, such as redness, swelling, and hard lump at the vaccination site, seek medical attention as soon as possible and inform the doctor of the vaccination. Ask the doctor to report the diagnosis to the local health department or the Centers for Disease Control.
  3. Although the chance of contracting COVID-19 can be reduced through vaccination, it is still possible to be infected. Vaccine recipients still need to monitor their health and observe epidemic prevention measures.

Most common side effects

Common side effects Frequency
Pain/tenderness at injection site 71.2%
Soreness/weakness 36%
Muscle ache 27.6%
Headache 22.2%
Diarrhea 15.1%
Swelling/induration at injection site 10.5%
Feeling sick and vomiting 7.7%
Redness at injection site 4.9%
Fever 0.7%

Other possible reactions

Adverse reactions Frequency
Itching, chills, rash, nasopharyngitis, oropharyngeal pain, palpitations at injection site Uncommon (≥1/1,000 to <1/100)
Facial nerve palsy*, high intraocular pressure Rare (<1/1000)

*During the safety follow-up period, one subject in the Medigen vaccine group reported acute peripheral facial nerve palsy. The subject experienced this adverse reaction 13 days after the second dose

Medigen ingredients

Medigen is a protein subunit vaccine with the recombinant spike protein (S-2P) antigen. This vaccine also contains excipients: CpG 1018, Aluminum hydroxide, Phosphate buffer solution.