Herd immunity & a second wave: Here's what you need to know, SA

As SA sees a decline in daily Covid-19 infections, health experts have warned against complacency, arguing relaxed attitudes could result in a resurgence of transmissions and a“second wave” of the pandemic.

But what is a second wave and herd immunity? University of Cape Town (UCT) epidemiologist Dr Jabulani Ncayiyana explains what they mean:

Second wave

“It is a resurgence in Covid-19 cases as the virus transmission returns or a new strain of the virus transmission. It is important to say we may have reached the peak, but we are not over the first wave,” he warned.

Herd immunity

“The proportion of people with immunity in a given population. Herd immunity is achieved when enough of a population has become infected with a virus or vaccinated against it to stop its circulation.”

Ncayiyana said herd immunity is impossible to achieve in the absence of a Covid-19 vaccine.

What is the likelihood of SA seeing a second wave?

Ncayiyana said a second wave is inevitable and human behaviour could contribute towards it.

“It depends on how many people have immunity. If fewer people were infected during the first wave, then it means more people could get infected during the second wave. If people stop using prevention measures like social distancing and wearing masks and hand hygiene [more could get infected],” said Ncayiyana.

Health minister Zweli Mkhize said the threat of a resurgence in Covid-19 infections remains, even with the notable decline in daily infections.

“With the threat of resurgence remaining very real, we would not want to repeat recent history witnessed in some countries and allow a second surge to wreak even further destruction.”

When is SA likely to get a second wave? 

Ncayiyana said it is difficult to predict precisely when SA could see the second wave.

“It all depends on how people behave. Travelling is less important, what is crucial is how people will behave; becoming complacent in maintaining prevention measures — social distancing, and wearing masks and hand hygiene.” 

Prof Salim Abdool Karim said that the response to whether SA is out of the woods is not clear cut. He expressed concerns about how the virus may respond in the coming weeks, despite a decline in infections.

He referred to other countries, including the US, Spain and Switzerland, which are experiencing a second surge.

“We need to be very careful, this is not the time for complacency. We need to maintain all our efforts. If we look at one of the key drivers, it is the need for our economy to restart. We need to get people back to work.”