Singapore’s media outlet Channel News Asia (CNA) has a series called ‘CNA Insider’, which features videos and interviews dealing with Singapore and Asian issues. They recently did an interview regarding COVID-19 vaccines with various doctors and specialist well-versed in the field of infectious disease and vaccinations.
Here are the 10 (plus 1) questions that were answered by the doctors and specialists:
Q1: Pfizer and Moderna vaccines – What’s the difference?
Prof Ooi Eng Eong (Duke-NUS Medical School): Essentially there is not much difference. Efficacy of both vaccines is about the same, at about 95%. The main difference lies:
- Number of days apart from 1st dose and 2nd dose: Pfizer is 21 days; Moderna is 28 days
- Dose of each vaccine: Pfizer is 30 milligram, Moderna is 100 milligram
Q2: S0, is Moderna’s vaccine 3x more potent than Pfizer’s vaccine?
Prof Ooi Eng Eong: No, it does not. The difference in the dose is a very practical issue. They had to make a guesswork as to where the sweet spot for the dose of the vaccine is going to be. Pfizer narrowed it down to 30 (milligram), Moderna to 100 (milligram). I think in reality it’s somewhere in between.
Q3: What explains the difference in the gap between the 1st and 2nd dose for the 2 vaccines? Does it matter?
Prof Ooi Eng Eong: It doesn’t matter. By and large, the rule fo thumb is that about a month apart is about right. If you stretch it out a bit more, it actually could be even better, because you are giving the immune system time to ‘learn’. The problem though is that people tend to forget to come back (for their second dose) if you stretch it out.
Q4: Does Moderna’s vaccine have greater side effects since it is at a higher dose?
Prof Ooi Eng Eong: It does look that way, at least in the phase 3 trial data, where especially on the 2nd dose, the side effects like the tiredness and fever all appear to be more common in the Moderna vaccine compared to the Pfizer vaccine. But we cannot be sure that it’s entirely due to the dose.
Q5: What causes the side effects from the vaccination?
Prof Ooi Eng Eong: It’s our immune response to the vaccine. The side effects are, in some way, a good sign that your immune system is reacting to the vaccine. But for those who did not experience any side effects, the data is showing that you are still getting a good immune response.
Q6: Why do people who are vaccinated still get infected?
Dr Leong Hoe Nam (Infectious Disease Specialist, Mount Elizabeth Novena Hospital): Now what we are seeing are actually mutants strains of the virus, which are quite different from the original strand. In fact, it’s like the syllabus that has been changed. So now, where I used to score 95 marks in the standard syllabus exams, I do worse off because it’s a totally different mutant, it’s a totally different syllabus. But even if we went back to the original strain, the efficacy is only 95%. Which means out of 100 people, 5 of them will still end up with an illness.
Q7: If that’s the case, what is the point of getting vaccinated?
Dr Leong Hoe Nam: Vaccination changes a severe disease to a mild disease, and a mild disease to an asymptomatic disease. So our responsibility is not just about not falling sick with COVID-19, but it’s also preventing the severe forms, which require oxygen or intensive care. Because eventually, you don’t want to destroy your hospital and healthcare system.
Q8: How long will my protection last?
Dr Leong Hoe Nam: Overall, about 30% of us will have very long lasting antibodies that will cope, and the other 70% won’t have enough antibodies. They will fall with time or their immune response never mounted adequately. In those cases, all the more you will need to remind the immune system by going for a booster vaccine. For the 30% of us, we are talking about years at least.
Eventually, I suspect we will all have to do a blood test for antibody levels. When the antibodies fall to a certain low level, we probably have to go for vaccination again.
Q9: How do booster shots work?
Dr Leong Hoe Nam: Booster shots work by jolting the memory of the immune system. Antibody levels fall, but when you do a booster shot, you shoot the levels very high. In fact, Superman high. When that happens, you’ll be able to fight the virus even if it was a mutant.
Q10: Are the booster shots interchangeable?
Dr Leong Hoe Nam: If you think about the science of vaccinology, you should be fine, because you are stimulating the same spike protein again. One good possible outcome is this: we may be able to find good matches of different vaccines that will exceed what we’ll be getting all along with the traditional 2 doses of the same vaccine.
Bonus Question: When can we stop social distancing and wearing of masks (just like in the past)?
Assoc Prof Hsu Li Yang (Infectious Diseases Programme Leader, NUS Saw Swee Hock School of Public Health): That’s like looking into the crystal ball. So we aren’t really very sure, but personally I don’t see this happening for the next 3 to 4 years at least. Even if we achieve 80% vaccination of the population, the countries around us will still not be anywhere near that. So, that means travel will still be limited for the large part.
See the video on CNA’s Facebook feed for the full interview by CNA Insider.
Final words from the MCA team
Singapore’s vaccination drive has been ongoing since start of the year. Other countries, like India and Philippines, are also on their way in vaccinating their residents. It is important to understand the similarities and differences between the different brands of COVID-19 vaccines so as to not have any misconceptions between the vaccines and how they work.
