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Each year about 40 000 people are hospitalised with influenza in South Africa and about 11 000 die of the virus. Spotlight interviewed Shabir Madhi, a leading professor in vaccinology, about the flu and its implications for the fight against the Covid-19 coronavirus
While South Africa’s battle against Covid-19 intensifies, another invisible enemy is fast approaching. As temperatures change and long summer days turn into cold winter nights, more and more people will get sick with influenza.
The government’s chief advisor on Covid-19, Salim Abdool Karim, encouraged people to get a flu vaccine as a way to lessen the burden on the country’s healthcare system.
With the health department facing a shortage of the seasonal vaccines, Spotlight spoke to leading vaccinology professor Shabir Madhi about how the vaccine works, who should get it and what it means for the Covid-19 pandemic.
Two million doses
“In the past, South Africa has procured about 1.2 million doses of the flu vaccine [each year] and often we haven’t been able to use all of the doses, says Madhi.
“This year we procured 2 million doses and because of Sars-CoV-2 and all the hype around it, many people, myself included, are strongly recommending that people at least get the flu vaccine to mitigate some of the effects of Covid-19, especially people at high risk of severe disease.”
He explains that during each flu season bed occupancy at hospitals goes up to 80% or 90%, but this pressure could be significantly reduced if people get vaccines.
“It’s a good thing that we’ve ended up having a shortage because it shows that people have really been buying into that message and they did get vaccinated. Hopefully this is a positive legacy of Covid-19,” Madhi says.
How the vaccine works
The flu vaccine works by giving our bodies the necessary tools they need to fight off the flu virus. Madhi, who is director of the SA Medical Research Council’s respiratory and meningeal pathogens research unit, explains that the vaccine trains the immune system to produce antibodies to the head of a specific protein on the surface of the flu virus, called hemagglutinin.
The head of this hemagglutinin is what our immune system responds to.
When the virus infects cells and makes us sick, the hemagglutinin binds the virus to our cells, sort of like a glue.
The flu vaccine provides the body with antigens, which results in our bodies producing antibodies – strong proteins that help our cells fight the head of the hemagglutinin.
If the head of hemagglutinin can be defeated by these antibodies, we won’t become sick with the flu because the virus has no way of binding to and infecting our cells.
“The mutations in the head portion of [the hemagglutinin] is what actually drives the diversity of strains,” says Madhi.
“We have gradual changes that take place in the head of the protein, which makes for a slight drift [change] in the genetic composition of the virus, which makes the predictability of the virus difficult. If there’s too much drift from what [strains were] anticipated then [the vaccine] becomes less effective, but if there isn’t too much mutation then the vaccine will be more effective,” says Madhi.
How the vaccine is made
New flu vaccines have to be made each year to reflect the mutations and different strains of the virus around the world.
A key element of these vaccines is what specific antigens they contain.
Broadly defined, an antigen is a molecule that causes an immune response in the body.
Madhi explains that each year World Health Organisation reference laboratories collect flu virus samples and submit them for genetic sequencing at central facilities.
Once the samples are sequenced, using a predictive model, scientists work to predict which are the most likely strains that will circulate in the next flu season in a specific region.
Read: How genetic sequencing works and how it’s helping scientists fight Covid-19
“The selection of the strains is done through predictive modelling based on historical data looking at mutations that are occurring in the different strains of the virus. There are three important strains – H1N1, H3N2 and Flu B. With Flu B, there’s two major dominant lineages, which are Victoria and Yamagata strains,” says Madhi.
He explains that flu vaccines can either be trivalent, meaning they provide antigens for three strains, or quadrivalent, which provides antigens for all four.
The difference between the vaccines is that a quadrivalent one offers antigens for two Flu B strains, one from both lineages, instead of one.
“Most of the vaccines in South Africa are trivalent, but this year there has been an imported quadrivalent vaccine as well. What we do know of the trivalent vaccine, especially in adults, is that there is cross-protection between the lineages [such as Flu B lineages, Yamagata and Victoria]. So even though the lineage included in the flu vaccine might be [different] from the lineage which eventually starts circulating in a country, there is some protection between the lineages. It’s not an absolute requirement to have a quadrivalent vaccine to have protection against a lineage which is not included in a vaccine, for Flu B specifically.”
How much protection does a vaccine offer?
While a vaccine’s purpose is to equip our bodies to fight influenza, a specific year’s vaccine’s effectiveness depends on whether the circulating strains match what was predicted in the vaccine. Madhi says that in a good year the vaccine could be roughly 72% to 75% effective.
However, should there be a mix-match of circulating strains and what is offered in the vaccine, this effectiveness could drop to 20%.
“[In recent year] South Africa has seen more than one vaccine strain circulating. It might be H1N1 and some H3N2, or it might be H1N1 and Flu B, and that might come at different times of the winter season,” he says.
The vaccine’s effectiveness also depends on age group.
While the general population may experience 72% to 75% effectiveness, those over the age of 65 need a high dose of the vaccine, which is about three times the strength of the standard vaccine.
“[The effectiveness of the standard flu vaccine] probably drops to around 45% to 50% in the elderly, which is obviously a concern because the elderly are one of the high-risk groups for severe disease.”
Young children and the elderly
“The highest burden of severe disease from flu occurs in the two extremes of age – under the age of one and above the age of 65, who would require hospitalisation,” says Madhi.
South Africa sees about 11 000 deaths and 40 000 hospitalisations for flu each year.
According to Madhi, one third of South Africans will become infected, but only 1% to 3% of those people will have symptomatic illness, meaning they will experience fever, headache and/or sore throat.
“After people become infected, the risk groups for [developing severe disease include] the extremes of age, people with chronic lung disease [including TB], people with chronic heart disease, people living with HIV, and pregnant women, especially those in the second and third trimester of pregnancy,” he says.
So far, these risk groups as well as healthcare workers have been prioritised to receive flu vaccines by the health department.
Currently, there is no licensed vaccine for children under the age of six months, and the only way to protect them is to vaccinate their mothers during pregnancy.
“We’ve shown in our studies that when you do that you get similar protection in the babies in the first three months of their lives. In the first three months of life, babies [whose mothers have been vaccinated] are 85% less likely to develop illness than babies who are born to mothers who haven’t received a flu vaccine,” adds Madhi.
He said the adult vaccine only worked about half as well for children aged six months to nine years, and children who had not previously received the vaccine would need two doses one month apart.
He added that children in this age group were not considered a priority or an at-risk group for the vaccine.
Flu vaccines and Covid-19
While the flu vaccine won’t protect people from becoming infected with Sars-CoV-2 and developing Covid-19, scientists are concerned that should an individual become infected with both Covid-19 and the flu they might develop a severe illness.
“But that is purely hypothetical,” says Madhi.
“What we don’t know, at this point, is whether when there are two viruses circulating at the same time co-infection results in more severe disease or not. There’s no data to support that.”
He says studies are under way in both China and North America to obtain supporting data.
“If there’s a synergy between these two viruses in terms of how they cause disease, then it can happen that someone who didn’t receive a flu vaccine might be susceptible to developing the more severe Covid-19, which might have been mitigated by receiving a flu vaccine.”
But he is quick to point out that this is hypothetical.
How Covid-19 is changing the behaviour of other diseases
“Even without the annual flu, our healthcare systems are going to be split beyond capacity when we get an upsurge in Covid-19 cases irrespective of what plan we make and how much we’re planning to delay the epidemic. That’s the unfortunate reality,” says Madhi. “Having [the Covid-19 pandemic] concurrently with the flu will just compound the situation.”
As a result of the lockdown, he says the natural epidemiology of Sars-CoV-2 is changing in that the peak in case numbers has been delayed by six to eight weeks.
“Rather than peaking in May, we will start to peak in the middle of July or August. Hopefully by then the flu virus will start disappearing in South Africa, but it might be that the lockdown and closure of schools have also affected the behaviour of the flu virus this year,” he said.
What Madhi emphasises reiterates what Karim previously said, that the lockdown has bought South Africa some time.
“South Africa is not on a unique trajectory with what’s going to occur from Covid-19. We have only changed the epidemiology by sort of delaying it,” he says.
“Everyone should [get a flu vaccine], but in the context of there being a shortage we highly recommend the prioritisation of who receives the vaccine, including those individuals who are specifically at high risk of Covid-19.”
People in South Africa can get the flu vaccine at their local public clinic and private facilities through medical aid or out of pocket.
Spotlight has also seen the vaccine, both trivalent and quadrivalent, available at some private pharmacies.
This article was produced by Spotlight, an online publication monitoring South Africa’s response to TB and HIV
