The covid-19 pandemic has upended the lives of billions of people since it struck the Chinese city of Wuhan in December 2019. Official tallies reckon that it has caused 147m infections and led to the deaths of 3.1m people. The true toll may be higher still. Vaccines to combat sars-cov-2, the virus that causes the disease, have been developed in record time. So far 170 countries have mass-vaccination programmes underway and together they have administered about 1041m jabs.
In Malaysia, the latest vaccination rate is 22,903 doses per day, on average. At this pace, it will take another 5.7 years to cover 75% of the population.
Source : Bloomberg
Covid-19 vaccination has become the focus of many not just in the nation but also internationally. We look to it as one of the mechanisms by which we can return to more social and community interactions.
With vaccination, we will still have to wear our masks and limit the number of people in certain areas but we can move about more freely and life can return to a closer semblance of “normality”. However, for this to happen we will require vaccination to give us herd immunity.
What is herd immunity?
Herd immunity is where a sufficient proportion of the population has achieved immunity against Covid-19 through vaccination and this significantly reduces the spread of the disease and also protects those that cannot be vaccinated (contraindicated). Figure 1 illustrates this.
We are aware that the vaccines are effective at reducing hospital admission and clinical infection but the data is still uncertain as to how good they are at preventing transmission. Overall, it would result in a huge reduction in symptomatic cases, long-term morbidity and deaths.
To achieve herd immunity, a substantial proportion of a population would need to be vaccinated but we are currently uncertain as to what this percentage is. In some diseases like measles, 90-95% of a population need to be vaccinated to achieve herd immunity; in others like polio, we require about 80%. It is very likely that for Covid-19 we will require at least 75-85% of the population to be vaccinated.
How can we achieve herd immunity?
To try and answer the question on how we can achieve herd immunity, Figure 2 roughly illustrates the population of the country. Approximately 30% of our population of 32 million are below 18 years of age and currently not indicated for vaccination as the data for children is still not available.
At any one time we will have 2-3% of women who are pregnant or breastfeeding, and vaccination for this group will generally be deferred until later (unless they are in a high-risk situation). At least 1% of the population will be too ill, in hospital or have a contraindication to vaccination. I have assumed that a modest 10% will choose not to vaccinate.
This will leave us with the ability to vaccinate only 55-60% of the population; this is also assuming we are sensitive to our economic migrant and refugee populations that account for at least 10% of the population.
Hence, it can be seen that we will not be able to reach sufficient rates of Covid-19 vaccination in the population to reach herd immunity. Many countries realise this and studies are now being conducted on Covid-19 vaccination in children to see if we can increase the proportion of those vaccinated by involving them.
It is quite likely that we will end up vaccinating children down to 12 years of age. We must remember that, even if 60% of the population is vaccinated, when children go to school or kindergarten there is no herd immunity present in that environment (as all the children are not vaccinated). Herd immunity for children will currently only work when they are with many vaccinated adults.
Are we on target to achieve herd immunity?
As at March 17, 367,213 Malaysians or 1.15% of the population have been vaccinated with the first dose of a Covid-19 vaccine. In addition, 5,867,497 have registered to receive the vaccine, i.e. 30% of those eligible.
Only 15.8% of people over 60 years of age and those with comorbidities have signed up (target population for these groups is 9.4 million, but only 1.45 million registered). Both vaccinations and registrations are too slow.
Figure 3 shows our vaccination rate at present extrapolated to the end of the year. At the current rate of vaccination only approximately 6 million or 19% of the whole population will receive the first dose of the vaccine by the end of the year.
We expect that the health ministry, in partnership with the private sector, will ramp up vaccinations for Phase 2 that starts in April. The vaccination rate depends on vaccine supply, logistics and the capacity of the health system to deliver them.
In this pandemic that affects every single person, we need to take personal responsibility. We cannot expect others to help control the outbreak for us. We are in this together and our collective vaccination is part of the way forward.
Source : FMT