COVID-19 is the disease caused by a new coronavirus called SARS-CoV-2. COVID-19 spreads mainly by droplets or aerosols from the nose or mouth of infected person. The onset of symptoms is around 2-14 days. The symptoms of COVID-19 include fever, fatigue, headache, runny nose, sore throat, cough, loss of taste or smell. Some people may experience severe symptoms like pneumonia and death.
 

What is mRNA COVID-19 vaccine?

COVID-19 vaccines come from various technologies of vaccine manufacturing. The mRNA COVID-19 vaccines use genetically engineered mRNA to give your cells instructions for how to make the spike protein found on the surface of the COVID-19 virus. After vaccination, your immune cells begin making the spike protein pieces and displaying them on cell surfaces. This causes your body to create antibodies that will fight the SARS-CoV-2 virus. Thailand has approved two mRNA COVID-19 vaccines as the following:

• COMIRNATY^TM (Pfizer-BioNTech)
• SPIKEVAX^TM (Moderna)

 

Efficacy of the vaccine

 

Vaccine	Efficacy data of vaccine
COMIRNATYTM (Pfizer-BioNTech)	·        93-95% effective in preventing symptomatic COVID-19 infection. ·        95-100% effective against severe COVID-19 disease. (The efficacy of vaccine may vary from country based on clinical trial results)
SPIKEVAXTM (Moderna)	·        82-94 % effective in preventing symptomatic COVID-19 infection.

 

Who should get the COVID-19 vaccine?

People who are at risk of COVID-19 infection such as medical personnel as well as workers and officials tasked with disease control or are in contact with patients, and people who are at risk of severe COVID-19 disease such as elderly, obesity, and those with lung disease, heart disease, diabetes mellitus, immunocompromised, stroke, cancer, etc.

Each mRNA COVID-19 vaccines has indication in different population as the followings:

 

Age	Vaccine
Children 6 months to 4 years of age.	COMIRNATYTM (Pfizer-BioNTech) 3 micrograms/dose
Children 5 to 11 years of age.   For SPIKEVAXTM (Moderna), recommend for 6 to 11 years of age.	COMIRNATYTM (Pfizer-BioNTech) 10 micrograms/dose   SPIKEVAXTM (Moderna) 50 micrograms/dose
12 years old of age and older	COMIRNATYTM (Pfizer-BioNTech) 30 micrograms/dose SPIKEVAXTM (Moderna) 100 micrograms/dose

The safety and efficacy of COVID-19 vaccine in pregnancy and breastfeeding have not been yet established. Breastfeeding and pregnancy after the first 12 weeks could be considered to receive the COVID-19 vaccine but after a discussion of the benefits and risks with their healthcare professional.
 

How the COVID-19 vaccine is given?

Vaccines are injected intramuscularly following the schedule as below:

 

mRNA COVID-19 Vaccine	Dose and schedule (Primay series)
	Dose (milliliter)	Number of doses	Interval between 1st  and 2nd dose	Interval between 2nd and 3rd dose
COMIRNATYTM (Pfizer-BioNTech)
3 micrograms/dose	0.2	3 doses	3-8 weeks	8 weeks
10 micrograms/dose	0.2	2 doses	3-12 weeks	*
30 micrograms/dose	0.3	2 doses	3 weeks	*
SPIKEVAXTM (Moderna)
50 micrograms/dose	0.25	2 doses	4-12 weeks	*
100 micrograms/dose	0.5	2 doses	4 weeks	*

*People who are moderately or severely immunocompromised, the third dose (in primary series) is recommended by at least 4 weeks apart from the second dose.
For booster vaccination, mRNA vaccines are recommended vary based on age, primary series product. It is recommended to administer at least 3 months after completion of the primary series.
 

What if people cannot get the COVID-19 vaccine on schedule?

If people miss a scheduled injection, your doctor will decide when to give the missed injection. Please follow the instructions of your doctor, pharmacist, or nurse regarding follow-up injection.
 
 

Who should not get COVID-19 vaccine?

• Anyone who has had a life-threatening allergic reaction to COVID-19 vaccine or any component of the vaccine.
• Anyone suffering from an acute severe febrile illness. However, the presence of a minor illness, such as cold, and/or low-grade fever should not delay vaccination.

 

Who should be special precautions for the COVID-19 vaccine?

• Anyone who has an immunocompromised disease such as HIV (human immunodeficiency virus), or take a medicine that affects the immune system (such as high-dose corticosteroids or chemotherapy) because it is not known whether individuals with impaired immune responsiveness will elicit the same response as immunocompetent individuals.
• Anyone with thrombocytopenia, any coagulation disorder or to persons on anticoagulation therapy, because bleeding or bruising may occur following an intramuscular administration.

What is the common side effects?

The most common side effects after getting the vaccines were pain, swelling, itching, or redness at the injection site, followed by fatigue, headache, muscle pain, fever, chills, and nausea. Most of which are mild or moderate and go away within a few days on their own. No data on long-term side effects.

Specific side effects of each COVID-19 vaccine

• COMIRNATY^TM (Pfizer-BioNTech) has side effects listed below according to the following frequency categories:

 

Frequency	Side effects
Very common (≥1/10)	Injection site: pain, swelling Chills, fatigue, fever, headache, myalgia, arthralgia, diarrhea, Irritability (in 6-23 months of age)
Common (≥1/100, <1/10)	Injection site: redness Nausea, vomiting
Uncommon (≥1/1,000, <1/100)	Lymphadenopathy, Hypersensitivity reaction e.g. rash, pruritus, urticarial, angioedema)
Rare (≥1/10,000, <1/1,000)	Acute peripheral facial paralysis
Unknown frequency	Anaphylaxis Myocarditis, pericarditis**

 

• SPIKEVAX^TM (Moderna) has side effects listed below according to the following frequency categories:

 

Frequency	Side effects
Very common (≥1/10)	Injection site: pain, swelling Chills, fatigue, fever, headache, myalgia, arthralgia, nausea, vomiting
Common (≥1/100, <1/10)	Injection site: erythema, urticarial, rash
Uncommon ≥1/1,000, <1/100)	Injection site: pruritus
Rare (≥1/10,000, <1/1,000)	Acute peripheral facial paralysis, facial swelling
Unknown frequency	Anaphylaxis, hypersensitivity Myocarditis, pericarditis**

**Cases of myocarditis and pericarditis have been reported rarely and usually have occurred within 14 days after vaccination. It is mostly reported in male adolescents and young adults, especially after getting the second dose of the two mRNA COVID-19 vaccines. Available data suggest that the course of myocarditis and pericarditis following vaccination is not different from myocarditis or pericarditis in general.

Vaccinees (include parents and caregiver) should seek immediate medical attention if develop symptoms indicative of myocarditis or pericarditis such as (acute and persisting) chest pain, shortness of breath, or palpitations following vaccination.
 

What if severe side effects occur?

If abnormal symptoms occur such as rash, face or throat swelling, breathing difficulty, chest pain, arm or leg weakness, please go to the hospital immediately.
 
 

Drug interactions between COVID-19 vaccine and others

There is limited data available about the concomitant used of mRNA COVID-19 vaccine with other vaccines. However, the mRNA COVID-19 vaccine can be given with other vaccines at the same day or separately without specific interval recommendation.
 
 

Remarks

• Observe side effects at the hospital for at least 15 minutes and then continue to observe side effects at home.
• If you experienced any side effects, please inform the doctor, pharmacist, and medical personnel before getting next COVID-19 vaccine.
• Vaccine cannot protect you entirely from COVID-19 disease but it can protect you from severe COVID-19 disease. Therefore, people who get the COVID-19 vaccine can be infected without symptoms or mild symptoms. You need to maintain to comply with prevention measures such as social distancing, wearing a face mask, and frequently washing hands.
• Get a vaccine as schedule and keep the vaccine record with you.
• If you have any further questions about COVID-19 vaccines, you can ask your doctor, pharmacist, or medical personnel.

 

References

• Comirnaty [package insert]. Bangkok: Pfizer; 2022.
• Spikevax COVID-19 Vaccine Moderna [package insert]. Bangkok: Zuellig Pharma Ltd.; 2022.
• Centers for Disease Control and Prevention. Pfizer-BioNTech COVID-19 Vaccine Overview and Safety. Available from: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/Pfizer-BioNTech.html. [Accessed 8 October 2022].
• Centers for Disease Control and Prevention. Moderna COVID-19 Vaccine Overview and Safety. Available from: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/Moderna.html [Accessed 8 October 2022].
• Department of Disease Control. COVID-19 Vaccination Guideline in Thailand. Available from: https://ddc.moph.go.th/vaccine-covid19/getFiles/11/1628849610213.pdf [Accessed 8 October 2022].
• Thompson MJ, Burgess JL, Naleway AL, Tyner H, Yoon SK, Meece, J. et al. Prevention and Attenuation of Covid-19 with the BNT162b2 and mRNA-1273 Vaccines. N Engl J Med 2021;385:320-329.