The United States is closely watching the COVID-19 surge for clues

COVID-19 cases are surging in South Africa, and public health experts in the United States are watching the data closely, waiting to see what it might reveal about how immunity to previous infections behaves over time.

South Africa has been the leader before. Scientists there first identified the Omicron variant of the coronavirus late last year, setting off a global chain reaction. Cases in the country declined after the peak of the pandemic in December, but now they are rising again – along with positive rates and hospitalizations. This could be South Africa’s fifth wave.

The spike is linked to two new Omicron subfamilies, BA.4 and BA.5, which the World Health Organization added to its surveillance list last month. By the end of April, they dominated transmission in the country, accounting for nearly 60 percent of all new COVID-19 cases, according to South Africa’s National Institute of Communicable Diseases.

Scientists in South Africa have found that BA.4 and Ba.5 can evade previously infected antibodies well enough to trigger a new wave of infections, but are unlikely to do so in people who have been vaccinated against COVID-19. Almost all South Africans have been vaccinated or have been infected.

Each spike occurred about four to six months apart. This tells me that the natural immunity of the general population will weaken enough after four to six months to have another big surge.

Cases are rising again in the United States. According to new data from the US Centers for Disease Control and Prevention, nearly 60% of adults and 75% of children have antibodies that indicate they have been infected with COVID-19.

Health experts say it’s unclear what this means for preventing future infections, so the CDC says it’s still important to keep up to date with COVID-19 vaccines and booster vaccines.