Covid-19 Vaccination

The information on the COVID-19 changes every day and it is getting difficult for people to catch up with the latest situation.  Therefore, Marina Medical will like to contribute by providing what we have learned and organised them in a way that hopefully, you can understand and get yourself prepared. We will actively update on anything new that we have learned.

Written by Dr Ivan Chow 

Information from the World Health Organization, UpToDate Inc, Pfizer, Moderna, AstraZeneca, the Lancet, The New England Journal of Medicine, Hong Kong Government, 

Declaration of Interest: Nil

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Latest Update
Latest Update

Latest update from government on Addition Booster for 2023

Updated on 8 June 2023

Citizens belonging to the following priority groups,
if they have completed the initial doses, they can receive an additional vaccine booster at least 180 days after their last dose or COVID-19 infection (whichever is later) free of charge in 2023, regardless of the number of vaccine doses they received in the past:

  1. Individuals aged 50 or above (including elderly living in residential care homes)
  2. Persons aged 18 to 49 years with underlying comorbidities
  3. Persons aged 6 months or above and with immunocompromising conditions
  4. Pregnant women
  5. Healthcare workers




Self-financed BioNTech Bivalent Vaccination Service

Updated on 8 June 2023

Persons who meet the following conditions are eligible for the self-financed vaccination service:

  1. Persons aged 18 or above
  2. Completed the COVID-19 vaccine primary series

Bookings for vaccination with BioNTech bivalent vaccine now opens to eligible persons

Updated on 30 Nov 2022

Eligible persons aged 12 or above may choose to receive the BioNTech bivalent vaccine from December 1, and online reservations has been opened since November 27.

In view of the arrival of the Comirnaty Original/Omicron BA.4-5 bivalent vaccine on November 25, the online booking system has been updated to provide options for eligible persons when making appointment. Eligible persons aged 60 or above with same-day tickets may choose the type of vaccine to be administered on site.

The BioNTech bivalent vaccine can be used as an alternative to the fourth dose (or the third dose for recovered persons) for eligible persons aged 12 or above following the current vaccination schedule, while the Sinovac or the BioNTech ancestral strain vaccines can still be used. 

Book now:


Comirnaty bivalent vaccine is now authorised for emergency use in Hong Kong

Updated on 18 Nov 2022

The Government announced on November 18 that the Secretary for Health has authorised the Comirnaty Original/Omicron BA.4-5 bivalent vaccine (i.e. Comirnaty Original/Omicron BA.4-5 (15/15 micrograms)/dose Dispersion for Injection COVID-19 mRNA Vaccine (nucleoside modified)) by Fosun Pharma/BioNTech for emergency use in Hong Kong.

According to the information provided by the drug manufacturer, the first batch of the Comirnaty Original/Omicron BA.4-5 bivalent vaccine to be supplied to Hong Kong is expected to arrive Hong Kong from Germany at the end of this month. The Government will arrange for the Comirnaty Original/Omicron BA.4-5 bivalent vaccine to be used as an alternative to the fourth dose in accordance with the current vaccination schedule. Both types of vaccines currently provided (Sinovac and Comirnaty vaccines) can continue to be used as the fourth dose. After receiving shipment of the relevant vaccine and completing the necessary quality assurance procedures, the Government will provide the relevant vaccines to the public as soon as possible. Details will be announced later.


Minimum age for BioNTech jab lowered to 6 months

Updated on 16 Nov 2022

Starting from November 9, the four Children Community Vaccination Centres (CCVCs) will provide vaccination service to children aged between 6 months and 4 years with the toddler formulation of the BioNTech vaccine. Children have weaker resistance to diseases and they can fall into severe conditions should they get infected with the COVID-19 virus. They may also develop medium and long-term after-effects after recovery. Vaccination can reduce the risks of severe illness and death

As the toddler and paediatric formulations of the BioNTech vaccine for children require a special dilution procedure, children below 12 have to receive the BioNTech vaccine at the four CCVCs. There is no same-day ticket arrangement at the CCVCs and parents have to make prior bookings online.

Make an appointment for Covid-19 vaccination:


Minimum age for Sinovac jab lowered

Updated on 3 Aug 2022

The Government announced on Aug 2 that children aged from six months to three years can receive the Sinovac vaccine starting from Aug 4.

Based on related clinical trials and studies of vaccination for local adolescents, the experts considered that three doses of Sinovac vaccine can be used for children aged six months to less than three years, following the same schedule of vaccination for older children. For the BioNTech vaccine, experts advised a three-dose series to be administered to children aged six months to under five years, with each dose to be one-tenth of that for adults.

Reservation for free Sinovac vaccination can be made through the private doctors or clinics that participate in the COVID-19 Vaccination Programme. From 9am on August 4, parents and guardians can also make appointments online for children aged from six months to three years to receive a Sinovac vaccine at community vaccination centres or designated general out-patient clinics of the Hospital Authority.

Sinovac Covid-19 vaccination service is available at Marina Medical.



What is hybrid immunity?

Updated on 22 Jul 2022

According to the World Health Organization, hybrid immunity is achieved when a person receives at least one dose of a Covid-19 vaccine and has been infected with the virus before or after receiving their jab.

Why has hybrid immunity come into focus?

Covid-19 cases has been rising again since early June, after social-distancing rules were eased, with figures last week exceeding 3,000 cases per day. With the number of serious cases and related hospital admissions both increasing, the government has expressed concerns about the growing pressure on the healthcare system, which was overwhelmed during the peak of the fifth wave.

Four HKU pandemic experts, including two government advisers, last week called for authorities to achieve hybrid immunity before the winter to prevent another “catastrophic collapse” of the healthcare system.

How can a higher level of hybrid immunity be attained?

To achieve a higher level of hybrid immunity before winter, the four HKU experts have called for a further easing of social-distancing measures to boost the number of natural infections and increase immunity levels, while the city waits for vaccine manufacturers to produce an Omicron-targeted booster shot.

The HKU experts suggest the proposal to be carried out during the summer when the virus has a lower degree of environmental survival, will be less transmittable by air and infection has a smaller chance of causing inflammatory damage.


Children between aged 3-4 are eligible for Covid-19 vaccination

Updated on 14 Feb 2022

The Government announced on February 13 (Sunday) that the minimum age for receiving the CoronaVac (Sinovac) vaccine will be lowered to three years old starting from February 15.

Parents/guardians could arrange Sinovac vaccination for children through private doctors or clinics that participate in the Vaccination Programme, or vaccination at Community Vaccination Centres or designated general out-patient clinics of the Hospital Authority (registration begins on 15 February 2022, 8am at the COVID-19 Vaccination Programme website).  

An interval of 28 days is required for children to receive the first and the second doses of the Sinovac vaccine, the same arrangement as for adults.

Covid-19 (Sinovac) vaccine is available at our Central clinic. For further enquiries or appointment booking, please contact us at +852 3420 6622,  click here (Whatsapp), or email



Children and adolescents are eligible for Covid-19 vaccination

Updated on 19 Jan 2022

The Hong Kong government has announced to lower the Covid-19 vaccination requirement to cover aged 12 to 17 adolescents in 2021 Dec, and the government recently has announced will further lower the age requirement to children aged 5 to 11 years old. The scientific committees under the Centre for Health Protection have no objection to allowing the use of the Sinovac vaccine in children aged five to 11.

Arrangement of the Covid-19 (Sinovac) vaccination for children shall be available this week, and BioNTech vaccination for children shall be available after Chinese New Year. Details and arrangements are to be released by the Hong Kong government. 



Hong Kong Government advice on Covid-19 boosters

Updated on 3 Jan 2022

Below groups of individuals are eligible for the 3rd dose of COVID-19 vaccine:

Updates on Omicron

Updated on 20 Dec 2021

On 26 November 2021, WHO designated the variant B.1.1.529 a variant of concern and named it “Omicron”.

About Omicron 

It is not yet clear whether Omicron is more transmissible or causes more severe disease, but preliminary evidence suggests there may be an increased risk of reinfection with Omicron.



Severity of disease

Effectiveness of prior SARS-CoV-2 infection 




Increased risk of reinfection


Transmissibility: It is not yet clear whether Omicron is more transmissible compared to other variants, e.g., easier to spread from person to person. The number of people testing positive has risen in areas of South Africa affected by this variant, but epidemiologic studies are underway to understand if it is because of Omicron or other factors.  

Severity of disease: It is not yet clear whether infection with Omicron causes more severe disease compared to infections with other variants.  Preliminary data suggests that there are increasing rates of hospitalization in South Africa, but this may be due to increasing overall numbers of people becoming infected, rather than a result of a specific infection with Omicron. There is currently no information to suggest that symptoms associated with Omicron are different from those from other variants.  

Effectiveness of prior SARS-CoV-2 infection  

Preliminary evidence suggests there may be an increased risk of reinfection with Omicron. For example, patients who have previously had COVID-19 could become reinfected more easily with Omicron compared to other variants of concern. However, information is limited, and more information and studies are to be conducted.  

Source: WHO


Jab scheme to cover people aged 16 to 29

Updated on 16 Apr 2021

The Hong Kong Government announced the COVID-19 Vaccination Programme will be expanded to cover people aged 16 to 29. The minimum age for receiving the BioNTech vaccine is 16 and that for receiving the Sinovac vaccine is 18. The community vaccination centres (CVCs) are expected to operate until the end of September, and people wishing to receive the BioNTech vaccine have to get the first dose by the end of August.

Citizens aged 16 to 29 can make reservations starting from 9am on April 23 through the online booking system to receive vaccines at 29 CVCs and 18 general out-patient clinics of the Hospital Authority (HA) or make appointments for vaccinations with private doctors or clinics participating in the programme. Click here to view the vaccination priority group.



Covid-19 vaccination programme will open to 1.3 million more Hongkongers from Tueday

Updates on March 8th, 2021

Hong Kong’s city-wide vaccination drive will open to seven more priority groups from March 9th (Tuesday) onwards, Secretary for the Civil Service Patrick Nip announced on March 8th (Monday). It means the vaccination programme will now able to cover additional 1.3 million Hongkongers. 

The seven priority groups include staffers from eateries, supermarkets, markets, convenience stores, and those working food delivery. Transport workers were also prioritized for the inoculation program.

Construction workers, property management staff, school staff including school bus drivers and staffers from the travel industry were also included on the list.

As for staffers working at gym centres and the beauty industry, they can also make their booking starting tomorrow morning.  Click the link to view if you are eligible

source: GovHK


Updates over the 2 ready COVID-19 vaccines in Hong Kong 

Updates on February 22, 2021

We have updated the Vaccination comparison table to provide a more complete overview of the 2 available COVID-19 Vaccines in Hong Kong,(vaccine table)


Conclusion and Recommendation from Centre for Health Protection on 8 Feb 2021 regarding Covid-19 vaccineBNT162b2

Updates on February 16, 2021

There is currently no evidence suggestive of any unexpected or untoward increase in mortality in frail elderly following the use of COVID-19 vaccine by Fosun Pharma/BioNTech (i.e. Comirnaty COVID-19 mRNA Vaccine). There is also no clear evidence suggesting the reported deaths were due to the use of the vaccine. For most frail elderly, the benefit of reducing the risk of a severe COVID-19 disease course outweighs the risk of receiving the vaccine.

For elderlies with severe frailty (e.g. bedridden elderly), especially those at the most extreme age groups (such as those above 85 years old), any mild adverse event from pharmaceutical products including vaccines might worsen their original disease course or condition. The benefits and risks of receiving the vaccine in these particular groups should be evaluated separately by attending clinicians and such clinical assessment should be exercised with greater caution.

Any individual who is experiencing acute febrile diseases should delay their vaccination.

Currently, safety data on the use of the vaccine remains limited and long term data are lacking. As mass COVID-19 vaccination programs continue worldwide, information regarding rare adverse events and long term side effects will be emerging.


Pfizer-BioNTech COVID-19 vaccination (BNT162b2) data report by CDC

Updates on February 3, 2021 

According to the CDC, during December 14-23 2020, there were 21 cases of anaphylaxis after administration of a reported 1,893,360 first doses of the Pfizer-BioNTech COVID-19 (BNT162b2) vaccine (11.1 cases per million doses); 71% of these occurred within 15 minutes of vaccination.


Fosun Pharma-BioNTech vaccine (BNT162b2) arrival at end of Febuary 

Updates on January 27, 2021 

The Secretary for Food and Health (SFH) authorised the COVID-19 vaccine  (BNT162b2) by Fosun Pharma-BioNTech on January 25 for emergency use in Hong Kong. The vaccine fulfilled the criteria of safety, efficacy and quality for specified use in Hong Kong under emergency situation. According to the information provided by the vaccine supplier, the first batch of 1 million doses of the Fosun Pharma/BioNTech vaccine to be supplied to Hong Kong have completed production and are undergoing safety and quality testing. Subject to the completion and passing of the relevant tests, the relevant vaccines are expected to arrive in Hong Kong from Germany in late February. The territory-wide vaccination programme led by the Government will be launched as soon as possible after completing all necessary quality assurance procedures. 


Sinopharm vaccine proves its safety and effectiveness in Phase III clinical trial

Updates on January 23, 2021

About 200 politicians from Hong Kong travelled to Shenzhen on 22 Jan 2021 for a Covid-19 vaccination (Sinopharm). According to the news released from Sinopharm on 2 Jan 2021, in Phase III clinical trial efficacy rate is 79.34%. A large sample of injection and data prove its safety and effectiveness. Besides, the vaccine doesn’t require freezing temperatures for storage, making transport and distribution much easier. The vaccine requires two doses in 21 to 28 days apart.



Recommendation on COVID-19 vaccines in Hong Kong by The Scientific Committees

Updates on January 22, 2021

The Scientific Committee on Vaccine-Preventable Diseases and the Scientific Committee on Emerging and Zoonotic Diseases under the Centre for Health Protection of the Department of Health published the consensus interim recommendations on the use of COVID-19 vaccines in Hong Kong.
The current recommendations focused on two vaccines, namely BNT162b2 provided by Fosun Pharma/BioNTech and AZD1222 provided by AstraZeneca. 
The recommendations are summarised below:
Both vaccines consist of a schedule of two doses. Individuals should complete their vaccination with the same type of vaccine.

  • Priority should be accorded to high-risk groups that are most vulnerable to the development of severe disease or death from COVID-19 infection, have greater risks of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and transmitting the virus to susceptible and vulnerable patients, or are critical for maintaining essential societal functioning.
  • Priority has been suggested to be accorded to the following groups:
    First: Residents and staff of residential care homes for the elderly/persons with disabilities and other institutional facilities;
    Second: Workers in health-care settings, workers in other essential services who are at increased risk of exposure to COVID-19, and persons aged 60 years or above; and
    Third: Persons with chronic medical problems aged between 16 and 59 years.

Vaccination is only one of the tools in the overall public health response to COVID-19. There is a need to continue public health strategies on non-pharmaceutical interventions, including social distancing, good hand hygiene and wearing a mask in public, to reduce the risk of transmission.


Sinovac clinical study reported by The Butantan Institute and the Government of Sao Paulo 

Updates on January 20, 2021

The Butantan Institute and the Government of Sao Paulo report that the coronavirus vaccine (Sinovac) achieved a 50.38% overall efficacy rate in the clinical study conducted in Brazil, in addition to (an efficacy rate of) 78% for mild cases and 100% for moderate and severe cases of Covid-19.



Vaccination program begins by early Feb 2021 at 18 districts' vaccination centres 

Updates on January 7, 2021

Dr Thomas Tsang Ho Fai, a member of the government's vaccination program task force, said on a radio program that authorities plan to set up vaccination centres at 18 districts in the city and start the vaccinations early February 2021. The first batch of 1 million doses of vaccine is produced by Sinovac, a mainland pharmaceutical company.

According to Reuters, the vaccine developed by China’s Sinovac Biotech was 78% effective in a late-stage Brazilian trial with no severe COVID-19 cases. There is no detailed data available yet.


Hong Kong Government reached agreements with Sinovac and Fosun Pharma

Updates on December 11, 2020

The Hong Kong Government held a press conference on December 11, 2020. Hong Kong has reached agreements with two COVID-19 vaccine manufacturers (Sinovac and Fosun Pharma), securing 15 million shots, the first million of which could be available as early as January. 

The Government will soon reach a deal with a third manufacturer (AstraZeneca) which will also provide 7.5 million doses to the city.


Pfizer and BioNTech
Pfizer and BioNTech

Pfizer and BioNTech

On December 8, 2020, the United Kingdom has become the world's first nation to begin vaccinating its citizens with a fully vetted and authorized COVID-19 shot, a landmark moment in the coronavirus pandemic.[1]

On December 10, 2020, The New England Journal of Medicine has published safety and final efficacy results from Phase 3 trial of mRNA-based COVID-19 vaccine. It demonstrated the vaccine has an efficacy of 95%. Efficacy was consistent across age, gender, race and ethnicity demographics.

Side Effects

Local reaction including pain, swelling and redness at the injection site. Systemic events like fatigue, headache, muscle pain, and fever were reported, more often by younger recipients and more often after the second dose. For adverse events, 0.3% of recipients reported lymphadenopathy. No deaths were related to the vaccine.


Follow-up time was 2 months only, the duration is not long enough to detect less common adverse events. Moreover, the duration of protection remains to be determined.[2] 


The recommended storage temperature condition is -70°C for up to 10 days unopened. Then the vaccine can be stored at refrigerated 2-8°C conditions for 5 days.





Persons Eligible for Receiving Vaccination
Persons Eligible for Receiving Vaccination

Persons Eligible for Receiving Vaccination

updates on February 14th, 2022

Hong Kong residents

The minimum age for receiving the Sinovac vaccine has been lowered to 3 from 15 February 2022. The minimum age for receiving the BioNTech vaccine will be lowered to 5 from 26 February 2022.

Eligible persons please choose one of the following groups when making online booking at the designated website or appointment with private clinics participating in the Vaccination Programme for statistical purpose.

  1. Personnel in healthcare settings and those participating in anti-epidemic related work
  2. Residents and staff of residential care homes for the elderly / persons with disabilities and staff of Community Care Service units for the elderly / persons with disabilities
  3. Personnel maintaining critical public services (including employees of Government service contractors)
  4. Personnel providing cross-boundary transportation or working at control points and ports
  5. Registered construction workers and other resident site personnel
  6. Staff of local public transport service operators (e.g. taxi/bus/public light bus drivers, train captains and station staff)
  7. Staff of food and beverages premises, markets, supermarkets, convenience stores and couriers (including takeaway food delivery)
  8. Staff of property management (e.g. security guards, cleaning staff and property management office staff)
  9. Teachers and school staff (e.g. teaching and support staff of kindergartens, primary and secondary schools and universities; staff of special schools; and drivers and escorts of school buses and school private light buses)
  10. Staff of the tourism industry
  11. Staff of scheduled premises under the Prevention and Control of Disease (Requirements and Directions) (Business and Premises) Regulation (Cap. 599F) (e.g. staff of fitness centres and beauty parlours)
  12. Domestic helpers
  13. Accompanying person(s) that already received the first dose of vaccine
  14. Others (Persons who do not belong to any of the above groups)




On November 30, 2020, Moderna announced mRNA vaccine efficacy of 94.1% in Phase 3 study.[1] 

Side effects

Adverse events included injection site pain, erythema, redness, fatigue, myalgia, bone pain and headache which were generally short-lived.[2] 


The vaccine can remain stable at 2° to 8°C, the temperature of a standard home or medical refrigerator, for 30 days.



University of Oxford and AstraZeneca
University of Oxford and AstraZeneca

University of Oxford and AstraZeneca

On December 8, 2020, the Lancet has published safety and efficacy results of the replication-deficient chimpanzee adenoviral vector vaccine. In participants who received two standard doses, vaccine efficacy was 62.1% and in participants who received a low dose followed by a standard dose, the efficacy was 90.0%. .[1] 


The median follow-up time was 3.4 months. It has not been able to assess the duration of protection.

Side Effects

Pain at the injection site was the most common local side effects. For systemic side effects, fatigue and headache were the most reported. Others side effects include muscle ache, malaise, chills and fever.

Three cases of transverse myelitis were reported as suspected unexpected serious adverse reactions, with two in the vaccine study arm, triggering a study pause. Independent clinical review of these cases has indicated that 2 cases are unlikely to be related to study interventions, but a relationship remained possible in the third case.[2] 


The vaccine can be stored, transported and handled at normal refrigerated conditions (2° to 8°C) for at least 6 months and administered within existing healthcare settings.


[1] Merryn V, Sue ACL, Shabir AM, et al. Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK. Lancet. 2020; (published online Dec 8.)

[2] Folegatti PM Ewer KJ Aley PK et al. Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2: a preliminary report of a phase 1/2, single-blind, randomised controlled trial. Lancet. 2020; 396: 467-478



On November 17, 2020, the Lancet has published the safety, tolerability, and immunogenicity of CoronaVac, an inactivated vaccine (phase 1/2 clinical trial). Seroconversion of neutralising antibodies was 92%-100%.[1] Phase 3 trial results are not available yet.



Vaccines Comparison table
Vaccines Comparison table

Vaccines comparison table

Updated on 8 June 2023


Vaccine name




Fosun Pharma in collaboration with the German drug manufacturer BioNTech

Sinovac Biotech (Hong Kong) Limited

Technology platform

mRNA vaccine

Inactivated virus

Injection method






Mild cases 83.7%

Moderate and severe cases 100.0%

Severe cases 100.0%


Hypersensitivity to the active substance or to any other ingredient of this vaccine

Allergic reaction to any component of the vaccine or similar vaccines

Severe neurological conditions

Patients with uncontrolled severe chronic diseases

Pregnant and lactating women

Number of dosages



Interval between dosage

21 days apart

28 days apart


Individuals of 6 years old and older

Individuals of 6 years old and older


Not routinely recommended. Only be considered when the potential benefits outweigh any potential risks for the mother and foetus.



Not routinely recommended.



Animal studies do not indicate harmful effects

No data


COVID-19 vaccination Side effect




Injection site pain and swelling

Very common. More than 1 in 10 people

Very common. More than 1 in 10 people



Muscle pain

Common. Up to 1 in 10 people

Joint pain



Uncommon. Up to 1 in 100 people

Injection site redness

Common. Up to 1 in 10 people

Common. Up to 1 in 10 people


Enlarged lymph nodes

Uncommon. Up to 1 in 100 people


Feeling unwell

Pain in limb


Injection site itchy

Common. Up to 1 in 10 people

Temporary one sided facial dropping

Rare. Up to 1 in 1000 people


Severe allergic reaction

Cannot be estimated from available data


Burn in injection site


Uncommon. Up to 1 in 100 people



Common. Up to 1 in 10 people

Loss of appetite

Rhinorrhea and nasal congestion

Cough and sore throat

Abdominal pain and diarrhoea



Uncommon. Up to 1 in 100 people


Abnormal skin and mucosa




Dizziness and drowsiness

Muscle spasm


Rare. Up to 1 in 1,000 people

Eyelid edema


Abdominal distension and constipation

Ocular congestion, conjunctival congestion

Hot flashes


Bell's palsy^

^Observed past-anthroisation in Hong Kong


Very rare. Less than 1 in 10,000 people

Serious adverse event


Nil was identified up to February 3, 2021


COVID-19 vaccination Availability/logistics




Online booking

Available at Community Vaccination Centres only

Available at:

- Community Vaccination Centres OR

Designated private clinic

*Vaccination is available at our clinic. For online booking, please fill out personal information. Then, select "covid-19 vaccination" for service and "Central" for location (only central clinic is available for vaccination). 

Private clinics availability

Not available in private hospitals and clinics


*Vaccination is available at Marina Medical. For online booking, please fill out personal information. Then, select "covid-19 vaccination" for service and "Central" for location (only central clinic is available for vaccination). 

Priority Groups

Please click here

Vaccination records

- Paper vaccination records OR

- Download their electronic vaccination records via the "iAM Smart" mobile app, or through the “eHealth” mobile app



Updated on December 11, 2020

COVID-19 vaccination information


Type of vaccine




Pfizer and BioNTech




-70°C±10°C for up to 10 days unopened. 2-8°C conditions for 5 days.





-20°C for 6 months. 2°- 8°C for 30 days

University of Oxford and AstraZeneca

Replication-incompetent vector vaccines


62.1% - 90%

2° to 8°C for 6 months

When vaccines are ready to use?
When vaccines are ready to use?

When vaccines are ready to use? 

All vaccines must be proven safe and effective in large (phase III) clinical trials and a series of independent reviews of the efficacy and safety evidence is required.

Officials in individual countries decide whether to approve the vaccines for national use and develop policies for how to use the vaccines in their country based on the World Health Organization (WHO)  recommendations.

The vaccines must be manufactured in large quantities, which is a major and unprecedented challenge.

As a final step, all approved vaccines will require distribution through a complex logistical process, with rigorous stock management and temperature control.[1]



What are Phase III clinical trials?
What are Phase III clinical trials?

What are Phase III clinical trials? 

These trials are designed to determine whether the vaccines prevent a disease. Subjects enrolled in phase III studies are randomly assigned and blinded to receipt of either vaccine or a control preparation (or comparator vaccine). Vaccine efficacy in percent is the reduction in specific disease incidence among those who received vaccine versus those who did not.[1]

Phase III clinical trials may not answer several efficacy questions related to SARS-CoV-2 vaccination. These include:

  • Duration of protection from disease
  • The potential need for and timing of additional booster doses
  • Effectiveness in subpopulations not evaluated in the clinical trials
  • Impact on community transmission



What are the different types of potential vaccines for COVID-19?
What are the different types of potential vaccines for COVID-19?

What are the different types of potential vaccines for COVID-19? 

  • Inactivated vaccines (e.g. Sinovac) are produced by growing SARS-CoV-2 in cell culture then chemically inactivating the virus. The inactivated virus in the vaccine stimulates an immune response[1]
  • Protein-based vaccines, which use harmless fragments of proteins or protein shells that mimic the COVID-19 virus to safely generate an immune response.[1]
  • Replication-incompetent vector vaccines (e.g. AstraZeneca) use a different vector virus that has been engineered to not replicate in the human body and to express the viral protein. Many replication-incompetent vector vaccine candidates use adenovirus vectors. One drawback to vector vaccines is that pre-existing immunity to the vector can attenuate immunogenicity of the vaccine. This can be avoided by using viral vectors that are uncommon in humans, vectors derived from animal viruses, such as a chimpanzee adenovirus.[1]
  • RNA vaccines (e.g. Pfizer, Moderna) were the first vaccines for SARS-CoV-2 to be produced and represent an entirely new vaccine approach. Once administered, the RNA is translated into the target protein, which is intended to elicit an immune response. Since the technology is new, the ability to produce large quantities of RNA vaccines has not been previously tested, and some of the vaccines must be maintained at very low temperatures, complicating storage.[1] It was believed that injecting RNA into a person does not do anything to the DNA of a human cell.

Fig. 1 How are vaccines created?

Fig. 2 What happens after the vaccine enters our body?



Questions not yet answered:
Questions not yet answered:

Questions not yet answered:

  1. How long after immunisation does it take to be protected?
  2. What is the estimated duration of protection?
  3. Can the vaccines prevent transmission?
  4. How the efficacy of the vaccines be affected by the cold-chain breach?
  5. What are the long-term side effects of the vaccines?
  6. Are the vaccines effective against all strains of SARS-CoV-2?
  7. Are the vaccines effective in all age and ethnic groups?
COVID-19 Testing FAQs
Post-Covid Treatment

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