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COVID-19 Vaccines: A Helpful Guide to Understanding Each Vaccine



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Many of us will agree that to have a shot at ending this global crisis that is the COVID-19 pandemic and vaccines play a primary role. In fact, world leaders came up with a solution not just to accelerate the development and manufacture of COVID-19 vaccines. There’s a global effort to guarantee that everyone in the world will have access to these vaccines, which shows to be just as crucial.

By now, we’ve heard the many names of the COVID-19 vaccines across the news. Some Filipinos appear to prefer some brands over others. But how different are they really? Are others truly more effective than the rest? More importantly, are they safe?

To better understand the COVID-19 vaccines available today, let us try to look at some general facts. 

How Vaccines Work

Photo from Mayo Clinic Health System

Vaccines work by making a person develop immunity to a virus. In simple terms, a vaccine introduces a weakened or inactive version (antigen) of the organism or germ into one’s body. Then, the body will trigger an immune response to fight it off. So in the future, when that person encounters that antigen, his immune system will be able to recognize and fight it off.


Photo from Boston Children’s Hospital

It is important to know that the weakened version of the antigen will not cause the disease when you receive a vaccine. The COVID-19 vaccine will not even give you a positive test result of the illness, either through an RT-PCR or antigen test.

All approved COVID-19 vaccines have been carefully studied, tested, and are being monitored on an ongoing basis. Clinical trials involving tens of thousands of people are done to ensure a vaccine’s safety. Know that these approved vaccines have shown to be safe and effective in different groups, across different ages, gender, ethnicities, and even those with medical conditions.

However, it is important to get clearance from your doctor first before getting a COVID vaccine if you are pregnant (available data insufficient) or breastfeeding, have an allergic reaction to vaccines, living with HIV, or immunocompromised. Vaccine trials for children are also still underway. 

Side Effects

Side effects are also a valid concern of many. However, mild side effects are totally normal after receiving a vaccine. The reason is that your body’s immune system is learning to react to the antigen and the side effects are manifestations of how it reacts. These should go away after a few days.

Some side effects are mild to moderate, like slight fever and muscle aches. Having side effects is a good sign: it usually means that your body is stimulated to fight off the virus and that the vaccine is working. Still, having no side effects does not mean that your body is not working against the antigen.


Photo from Unsplash

Perhaps one of the most controversial points in all these talks about vaccines is their efficacy. How effective are the COVID-19 vaccines? To put it simply, people should understand that as of yet, no vaccine is 100% effective. Experts are still undergoing continuous “vaccine effectiveness” studies. What the vaccine does is that it helps protect people against, and reduces the risk of COVID-19 and its severe complications. Studies have shown that vaccines are working well in real-life conditions.

Now that we have a basis of our expectations, let’s drill down into the top COVID vaccines available today and the interim recommendations provided by the World Health Organization (WHO). 

COVID Vaccines

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1) Sinovac-CoronaVac

Beijing-based pharmaceutical company Sinovac developed the Sinovac-CoronaVac vaccine. WHO validated this vaccine for emergency use with the assurance that it is safe to use and meets the international standards for efficacy and manufacturing. It makes use of inactivated SARS-CoV-2 virus in the vaccine. It also has easy storage requirements and is easier to manage. 

Type: Inactivated vaccine

Recommended dosage: 2 doses (0.5ml); interval of 2-4 weeks

Efficacy: Efficacy of 51% against symptomatic SARS-CoV-2 infection, 100% against severe COVID-19, and 100% against hospitalization 14 days after the second dose (Brazil, Phase 3 Trial) 

New variants: 49.6% against symptomatic infection (P.1 Variant Manaus, Brazil); 49.6% after one dose (P.2 Variant, Brazil) and 50.7% after the second dose. WHO will update accordingly.

Other notes: Recommended for persons with comorbidities, lactating women; Not recommended for individuals with a history of anaphylaxis, persons with acute PCR-confirmed COVID-19, and those with body temperature over 38.5°C

Photo from Unsplash

2) Pfizer-BioNTech (BNT162b2)

The Pfizer-BioNTech vaccine developed by US pharmaceutical giant Pfizer and German biotech company BioNTEch was the first COVID-19 vaccine approved for emergency use. The vaccine, also goes by the vaccine name Comirnaty, is the second-most preferred vaccine by Filipinos, next to Sinovac.

Type: mRNA

Recommended dosage: 2 doses; interval of 21-28 days

Efficacy: 95% against symptomatic SARS-CoV-2 infection

New variants: Effective against virus variants based on available data

Other notes: It has been highly effective in the clinical trials at preventing COVID-19 among different groups: diverse age, sex, race, ethnicity, and even those with underlying medical conditions.

Photo from

3) Oxford-AstraZeneca

The Oxford-AstraZeneca COVID-19 vaccine, also known as Vaxzevria (formerly AZD1222), was co-invented by the University of Oxford and its spinout company Vaccitech. The vaccine is made up of another virus (adenovirus family) modified to contain the genetic material of the SARS-CoV-2 spike protein to trigger an immune response. It does not contain the virus itself and cannot cause COVID-19.

Type: Adenovirus

Recommended dosage: 2 doses (0.5ml); interval of 8 to 12 weeks

Efficacy: 63.09% against symptomatic SARS-CoV-2 infection

New variants: Strategic Advisory Group of Experts on Immunization (SAGE) recommends using this vaccine even if virus variants are present in a country. Countries should assess the risks and benefits considering their epidemiological situation.

Other notes: European Medicines Agency’s (EMA) safety committee concluded its preliminary review on the topic of blood clots and confirmed that the benefits continue to outweigh the risk of side effects. The vaccine is also not associated with the increase in the risk of blood clots, and there is no evidence of a problem with specific vaccine batches.

Photo from Unsplash

4) Sinopharm

The Sinopharm vaccine is produced by the Beijing Bio-Institute of Biological Products Co Ltd. Similar to the Sinovac vaccine, it uses an inactivated vaccine and has easier storage requirements.

Type: Inactivated vaccine

Recommended dosage: 2 doses (0.5ml); interval of 3-4 weeks

Efficacy: Efficacy 79% against symptomatic SARS-CoV-2 infection 14 or more days after the second dose; 79% against hospitalization. The trial was not designed to show effectiveness against severe disease in persons with comorbidities, pregnant, or in persons 60 years old and above. Women are also underrepresented in trials.

New variants: Vaccine not yet evaluated in this context

Other notes: Two more efficacy trials underway; no data available yet

Photo from Unsplash

5) Johnson & Johnson’s Janssen 

Janssen Pharmaceuticals Companies of Johnson & Johnson is safe and effective in people with hypertension, chronic lung disease, diabetes, obesity, and severe cardiac disease.

Type: Adenovirus

Recommended dosage: 1 dose (0.5ml) with a minimum interval of 14 days for other vaccines against other health conditions

Efficacy: 85.4% against severe disease and 93.1% against hospitalization; 66.9% against symptomatic moderate and severe SARS-CoV-2 infection

New variants: Effective against B1.351 Variant (South Africa) and P.2 (Brazil)

Other notes: US’s Vaccine Adverse Event Reporting System (VAERS) reported fainting events among nearly 8 million doses of J&J/Janssen vaccines administered. It is not clear whether these are caused by anxiety or associated with the vaccine.

6) Moderna (mRNA-1273)

Photo from Unsplash

ModernaTX, Inc. manufactured COVID Vaccine mRNA-1273, an mRNA vaccine granted emergency use authorization. Along with another mRNA-vaccine, Pfizer-BioNTech, Moderna is said to have a longer-lasting immunity against coronavirus. So long as the virus does not evolve from its current form (which is uncertain), vaccinated people may not need boosters.

Type: mRNA

Recommended dosage: 2 doses (0.5ml); 28 days apart

Efficacy: 94.1%, starting 14 days after the first dose

New variants: New variants including B.1.1.7 and the 501Y.V2 do not alter the vaccine’s effectiveness

Other notes: US’s Vaccine Adverse Event Reporting System (VAERS) reported fainting events among nearly 8 million doses of J&J/Janssen vaccines administered. It is still not clear whether these are caused by anxiety or associated with the vaccine.

All these COVID vaccines are still undergoing ongoing studies, with new data coming in. At present, information is still not enough to answer some of the most important questions like risks of transmission, how long the protection lasts, and efficacy against emerging variants.

In the meantime, WHO advises the public to continue practicing public safety precautions guaranteed to work against transmission and infection. Continue to wear your masks, maintain social distancing, do proper handwashing, practice good cough hygiene, and maintain good ventilation.

Moreover, WHO does not recommend one vaccine over another. Instead, experts say that the best COVID-19 vaccine is the one available to you.



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