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FAQs on COVID-19 vaccines


As Hong Kong prepares to start COVID-19 vaccinations in February, I would like to focus on some questions people frequently ask me about the new COVID-19 vaccines. Given that this is the fastest vaccination drive in human history, it is understandable that people are concerned about what is going into their bodies. It is important to address these questions/concerns honestly, otherwise they might contribute to vaccine hesitancy.

 Pfizer-BioNTech COVID-19 vaccine is prepared by a healcare professional in Jerusalem, Isarel. AP

1. Are COVID-19 vaccines really effective?

Response: Yes, they are. All three vaccines purchased by Hong Kong have demonstrated efficacy rates in phase 3 clinical trials, which exceed the pre-defined WHO criteria for defining a vaccine as effective. This means that they are good at protecting people from developing symptoms and severe illness due to COVID-19. References are included in the table below.

2. How long does the protection last?

Response: So far, we have only followed up vaccine recipients for a few months, so we don’t have a definite answer to this question.

However, vaccines definitely maintained efficacy for a 3-4 month period after second dose in clinical trials. Study participants are now being followed up to evaluate efficacy over longer periods.

Some research has showed that antibody responses remain high 3-months after second dose of the Moderna mRNA vaccine, suggesting durable protection for longer periods (citations in the table below). This is good news for other vaccines that generate a strong immune response initially.

3. Do the vaccines work against variants/ mutant SARS-CoV-2?

Response: Recently, variants of SARS-CoV-2 have emerged in UK, South Africa and other countries. Some scientists have expressed concern that these variants may be ‘resistant’ to immunity generated by COVID-19 vaccines. However, a recent paper confirms that N501Y, a mutation of concern, does NOT affect mRNA vaccine performance. This is likely to also hold true for other spike-based vaccine platforms. Effects of other mutations on vaccine performance are being urgently evaluated with results expected soon. Even if a mutant affects vaccine performance in the future, vaccines of certain platforms such as mRNA can be rapidly adjusted and redeployed to fit circulating strains.

4. These vaccines seem to be new technologies. Are they really ready for human use?

Response: Inactivated vaccines (like the SinoVac's vaccine) are based on time-honoured technologies that we currently use for our hepatitis A, polio and rabies vaccines.

mRNA vaccine technology has actually been around for nearly a decade. These vaccines have been used/ are being used in early-phase trials in humans for a variety of infectious diseases and as cancer vaccines for several years already. Phase I clinical trails for a mRNA rabies vaccine have been published in 2017 (Alberer M et al, Lancet, 2017). So, there is a reasonably long history of these vaccines being used in humans.

Chimpanzee adenovirus-vector vaccines have been studied during the Ebola epidemic in Africa. There is even safety/efficacy data for their use in children (citations in table).

5. The vaccines seem really rushed. Have companies and governments taken shortcuts?

Response: Traditional vaccine development is an inefficient process with lots of funding roadblocks, trial design issues and regulatory bureaucracy leading to long delays.

However, in response to COVID-19, vaccine development has been highly streamlined. Pre-existing sophisticated vaccine platforms have been rapidly deployed against COVID-19 using decades of research in SARS and MERS coronaviruses. The streamlined clinical trials have been of high standards with no corners being cut. Bureaucracy has been streamlined in view of the urgency of the situation. Production and distribution was worked out even while pending clinical efficacy.

This is exactly what you get when you combine cutting-edge science, smart planning and decent funding: a model of success for future pandemics and a great human achievement.

6. I heard the vaccines can change your DNA. Is this true? What about other unknown side effects?

Response: Not true. This concern usually comes up with mRNA vaccines. mRNA is like a instruction manual for building a protein which then rapidly degrades after fulfilling its function. It does not enter the cell nucleus and is not capable of modifying DNA. The expressed spike protein excites an immune response to the virus. It is estimated that 24 million doses of vaccines have been administered worldwide as of Jan 10, 2021. The short-term experience suggests generally excellent tolerability and safety. One concern is increased risk of allergy with mRNA vaccines compared to other vaccine types, but this is easily circumvented by choosing alternative vaccine types for those with history of severe allergy. Given the way these vaccines work, I find it unlikely that we are going to encounter unpredictable side effects in the medium-to-long term.

7. What about pregnant women and children?

Response: Vaccination of children and pregnant women should be delayed until there is clinical trial data available for these age groups. As most COVID-19 vaccines don't contain live virus, some countries have decided to encourage pregnant women to receive the vaccine. This should theoretically be quite safe. However, I don't think there is an urgency for pregnant women in Hong Kong to receive the vaccine until there is sufficient safety data for these groups.

I hope these facts can assuage some of the concerns of people on the fence about receiving COVID-19 vaccines. After all, we all want to make the best decisions for our bodies. If you have any questions about the vaccines I haven't addressed, feel free to ask below.

Insist on reliable facts when making your choice.

Have a good week.

(First published at the author's facebook)

Credit: Dr. Sid

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