Forty percent vaccine coverage in SA can prevent 9-million infections, say Harvard modellers

Getting vaccines into at least 40% of the population can prevent more than 9-million Covid-19 infections and more than 73,000 deaths in SA, say US modellers.

Fewer hospitalisations mean the cost of the vaccine rollout will be lower than the bill for  treating more unvaccinated people in hospital, according to a study led by Harvard Medical School and published in science magazine Nature. 

Lead author Krishna Reddy and his team said they used “a microsimulation model to evaluate clinical outcomes and cost-effectiveness of a Covid-19 vaccination programme in SA”.

They found that “vaccination programme implementation factors, including prompt procurement, distribution and rollout, are likely more influential than characteristics of the vaccine itself in maximising public health benefits and economic efficiency”.

What this means is the efficacy of vaccines is less important than how quickly and efficiently the rollout happens.

Reddy said their model showed vaccinating 40% of the population decreased deaths by 82% to 85%, and lowered total health costs by 33% to 45%.

So far, 38.09% of the adult population is vaccinated, according to the National Institute for Communicable Diseases.

The study has major implications for SA in light of the government decision in March to sell one 1.5-million doses of the AstraZeneca vaccine.

An in-depth analysis by vaccinology expert Prof Shabir Madhi, dean of health sciences at Wits University, found the lives of 18,000-22,000 elderly people could have been saved had the doses not been sold to other African countries. 

He said  the sale also fuelled vaccine hesitancy across the continent, leaving many doses unused until they ultimately expired.

Madhi’s and Reddy’s findings augment the validity of advice given by the World Health Organisation, which was that AstraZeneca vaccine be rolled out as quickly and efficiently as possible despite the reduction of its efficacy by a new variant at the time.

Said Reddy: “Much has been made about differences in the leading vaccine candidates and the impact of variants ... on vaccine effectiveness.

“However, we found that even with substantially lower vaccine efficacy than reported in clinical trials, vaccination programmes would prevent the majority of Covid-19 deaths compared to scenarios without vaccines.”

The researchers began working on their microsimulation model as very little data was available to inform vaccine rollout policies for low-income and middle-income countries.

Microsimulation uses computerised tools that perform detailed analyses using numerous  factors to try to predict how those factors will influence the outcome. 

“In this work, we used a microsimulation model to estimate the clinical and economic outcomes of Covid-19 vaccination programmes in SA, examining different implementation strategies that policymakers could directly influence,” said Reddy.

The modellers simulated Covid-19 specific outcomes over 360 days, including daily and cumulative infections (detected and undetected), number of deaths and years of life lost due to Covid-19.

They also included “resource utilisation”, which in this case meant looking at the number of general and intensive care unit beds that would be used under different scenarios.

And they estimated healthcare costs from the all-payer (public and private) health sector perspective. 

TimesLIVE