Data from the Western Cape show that 30% of the recorded Covid-19 cases were aged over 50 and these cases were responsible for 60% of hospitalisations. Vaccination strategies need to take this into account. The experience of the third wave, as for prior waves, has been brutal.

Data from the Western Cape Covid-19 dashboard.

Courtesy of the Western Cape Department of Health and Professor Mary-Ann Davies.

Yet these 30% of cases were responsible for a massive 60% of hospital admissions and a whopping 85% of Covid-19 deaths in the province.  Almost all the impact is therefore concentrated among those over 50. Almost all this damage could have been prevented, and could be prevented in future with an appropriate vaccination strategy.

If prior patterns hold, the fourth wave will start in early January and peak in late February.

We hear a lot of talk about a national target of vaccinating around 70% of the adult population (over 18) to mitigate the damage from a fourth wave. But is this the appropriate target at this stage? Is it achievable before early January? At the present rate of vaccination (142,000 daily averaged over October), reaching 70% will take about 100 vaccination days. We don’t have time to reach this target.

A risk-based strategy is vital.

We need to ensure that there is near full coverage of the over-50s before the fourth wave hits. 

So far  South Africa as a whole has abysmally low vaccination coverage.   Our World In Data has our coverage at just 23.2% for at least one dose, and  17.6% fully vaccinated for the population as a whole (59.7 million). For the adult population over 18, this increases to 35%. If we add in the 12- to 17-year-olds from this month the denominator will increase, which means the percentage vaccinated will decrease.

As in other countries, South Africa started vaccinating appropriately by focusing on the over-60s, and then the 50-59-year-olds to utilise the first available batches of vaccines. As more vaccines arrived, the opportunity to be vaccinated was extended to progressively younger age groups. We are now in the fortunate position of having sufficient vaccine supply. However, focus has been lost as to what percentage coverage of the most vulnerable group, the over-50s, has been achieved.

To date, only 61% of the over-50s have been fully vaccinated in South Africa. The coverage for the different provinces ranges from 47% to 72%. This is not high enough to prevent a severe fourth wave in this highly vulnerable demographic. We should be aiming at a goal of 90% or more for this group. 

The following graphs contrast two different vaccine strategies,  targeting 70% of the entire adult population, and 90% of the over-50 population, respectively. 

Vaccination data are taken from the National Vaccination Dashboard.  For population data I have used  the Thembisa Project rather than the StatsSA population projections for 2020 since I believe these to be more accurate

The number for 70% of the adult population still needing to be vaccinated for South Africa as a whole is a whopping 13.9 million  (ranging from 4.7 million for Gauteng to 186,000 for the Northern Cape).  

To achieve a target of 90% of over-50s vaccinated, the numbers still required are a much more modest 3.8 million nationally (ranging from  1.2 million for Gauteng to 60,000 for the Northern Cape). 

Yet achieving this modest target would effectively defang the fourth wave.  

How feasible is it to achieve these targets in the two to three months available to us before the fourth wave?  

The following graph shows how many days are needed in each case to achieve the 70% of adult population target versus the 90% of over-50s target. The assumptions here are based on vaccinations seven days a week and a rate of 142,000 per day (based on the October average).  

The average number of days to vaccinate 70% of the whole population is about 100 days. The range across the provinces is from 70 to 120 vaccination days.

However, achieving the 90% of over-50s target can all be done in about 20 vaccination days at the current rate of 142,000 per day.

Since two vaccination doses are required for full immunity, the number of days to achieve these respective targets must be doubled. It is, however, important to remember that just one vaccine dose confers substantial protection against severe disease, hospitalisation and death, and consequently the number of vaccination days would not be quite doubled to achieve significant prevention. 

The reader is left to adjust the number of vaccination days further should the daily vaccination rate drop, or hopefully increase. 

The message from these data is crystal clear. To beat the fourth wave we need to ramp up our vaccination drastically. More importantly, in the next two months we need to concentrate efforts on high coverage of the over-50s. This is the number one priority. It is also a highly achievable target at current rates of vaccination, and even at lower rates. We need to mobilise all governmental, social, civil and individual resources to persuade all of the over-50s who can be reached to take the vaccine, and to facilitate their doing so to the maximum extent possible, whether by bringing the vaccine to them or bringing them to the vaccine. 

Of course, given that we have a sufficient supply of vaccines now,  anyone who wants to be vaccinated at other eligible ages should be encouraged and assisted to get vaccinated. There also appears to be capacity to provide many more vaccines daily than the 142,000 in the assumptions used here, and which appears to considerably exceed current demand.

But let’s get the over-50s done to the fullest extent possible as a matter of urgency. Let’s go out and persuade anybody we know who is over 50 and not yet vaccinated that this is the best thing they can do right now for the sake of their health. Let’s act now to take the pressure off the health services come January/February.  

Let’s all get this done together. 

Below is a table where you can find the number of over-50s still needing to be vaccinated in your province for 90% coverage. DM

Jonny Myers is Emeritus Professor in Public Health Medicine, University of Cape Town.