Q&A: Just how safe will SA’s vaccines be?
Scientists estimate that vaccines will provide two to three years of immunity
Vaccinations are expected to be rolled out in SA from April. But there are plenty of questions about how this will work.
Two of SA’s renowned experts on vaccines — Prof Glenda Gray, president and CEO of the SA Medical Research Council, and Wits professor of vaccinology Shabir Madhi, who ran Oxford’s AstraZeneca trial in SA — answered questions on the subject at two recent webinars hosted by Daily Maverick last week.
Predictably, many questions revolved around the safety of these vaccines, given how fast trials were conducted. Reports of 23 frail and elderly people dying in Norway after being vaccinated, as well as a small number of people suffering severe anaphylactic shock, have heightened these concerns.
Do we know enough about the safety of vaccines?
Gray explains that a headache and pain in the arm after the shot are the most common side effects.
“These normally start in the first few days after vaccination, and very rarely after weeks of vaccination,” she says.
The short-term safety data, which is available in this case, normally reflects long-term safety as well, Gray says. But in this case, long-term safety data is still being collected.
However, vaccinations will have to happen in a controlled health-care environment, with equipment available in the (exceedingly unlikely) event of a patient developing a severe allergic reaction.
Why get vaccinated when so many people have had the virus already? Wouldn’t their natural immunity protect them?
Madhi says the studies of people who developed Covid-19 show that their immunity to the illness (or at least to the same variant) lasts nine months.
“But the reason we only say nine months, up to now, is because most of the studies have only evaluated up to nine months.”
Typically, people who develop immunity to other coronaviruses which cause colds find that their immunity lasts two to three years. This has led some to think that people who have been very ill with Covid-19 may have immunity to the same strain for up to three years, says Madhi.
What about herd immunity? If so many people have had Covid-19, do we need vaccines?
SA does not yet have population-specific serology data of how widespread infection has been. The estimate from Discovery Health is that 40% of South Africans have had Covid-19. But without hard data, it is difficult to decide who needs the vaccine.
Additionally, vaccines may provide another layer of protection to people who have Covid-19.
“Vaccines really are designed to result in a much more predictable immune response. In natural infections, there is huge variability between individuals, depending on the severity of the illness,” Madhi says.
People who get very ill with Covid-19 typically have a much more robust antibody response than those who have had a mild infection or no symptoms at all.
But vaccines would provide everyone with a more equal degree of protection, and could provide a longer period of immunity than you would typically have after a mild infection.
How long will vaccine protection last?
Madhi says that right now, “it’s difficult to estimate exactly what the duration of vaccine-immune protection is going to be”.
The estimate, he says, is that vaccines will provide two to three years of immunity.
“But the big unknown that can surprise us, unfortunately, is how these vaccines are going to work specifically against new variants of Covid-19.”
Why are there so many variants?
The SA variant of SARS-CoV-2 is considered far more transmissible than the original version, and is believed to have been largely responsible for the rise in infections during the second wave.
Madhi explains that this second variant may have arisen because so many people in SA had been infected during the first wave that the virus had to mutate to survive.
“One of the main reasons this has probably emerged in SA [is that] the first time we had a high [rate] of infection. A large percentage of the population became infected. And the virus, to be able to survive, needs to somehow evade the immune response that was induced against it,” he says.
How does vaccination help stop new variants emerging?
Madhi says that to prevent further variants developing, you need to ensure that a large number of people become immune to the disease in a short time. This halts the virus from trying to evade the immune system by mutating.
Vaccines are the fastest and safest route to large-scale immunity.
Does vaccination actually stop the virus being transferred?
This is unclear, since the trials didn’t actually test this.
The trials weren’t designed to examine whether the vaccines stop the spread of Covid-19; the aim was to prevent a severe response in those infected.
As Pfizer CEO Albert Bourla has said, there is no certainty about whether vaccination will stop the spread of disease.
Still, scientists think that by preventing a severe response in people, it will prevent the virus transmitting as easily — but only if enough people are vaccinated.
On this score, the rollout of vaccines in Israel is being monitored to see if the incidence of Covid-19 falls, as a large percentage of the population has been vaccinated.
How can we use the Pfizer vaccine data in SA when that vaccine needs to be transported at -70°C?
Gray thinks Pfizer’s vaccine will be improved over time.
“The beauty about vaccine research is [that] once you learn that a vaccine works, you strive for innovation, and your next aim is to make your vaccine as stable at better temperatures,” she says.
She says the Moderna vaccine is similar to the Pfizer vaccine, even if it doesn’t require extreme refrigeration. And the second- and third-generation Pfizer vaccines may not require such extreme refrigeration, as Pfizer will look to improve the vaccine to reach a wider market.
The AstraZeneca vaccine arriving in SA this week does not require such cold temperatures. And the vaccine developed by Johnson & Johnson only requires a temperature of between 2°C and 8°C — though those trial results have not yet been released.
Will vaccination lead to zero Covid?
No. There has only ever been one virus that has been eradicated: smallpox.
But while Covid-19 will not disappear any time soon, it is hoped that in future, people will get only mildly ill.
Madhi says the “immunity threshold” — when enough people have had the virus or been vaccinated — will not stop the disease, though it will probably stop mass outbreaks.
“There shouldn’t be any delusions that Covid-19 is going to [go] away once we get to herd immunity of certain populations … It will probably be with us for decades to come. But what we try to avoid when we talk about herd immunity is the effects of resurgences that we are currently experiencing.”
Why were vaccines developed so fast?
Trials usually take place in three phases, both for safety and to assess the signals of the vaccine’s effectiveness. Phases two and three are larger, often a few years apart.
Drug companies won’t invest in the third phase of trials — which takes place in multiple locations with thousands of people and costs millions of dollars — unless they have a proof of concept and the safety from smaller trials is clear.
In this case, the vaccine trials took place simultaneously at different companies, which were far more open to taking on greater risk of these trials failing, given the imperative to halt Covid-19.
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