A tougher flu season is expected, but has not yet returned to pre-Covid levels

Health experts predict that this year’s flu season in South Africa will be much less serious than last year’s, but not much more serious than the pre-pandemic flu season in Covid-19.

According to the National Institute for Infectious Diseases (NICD), the number of cases of influenza will increase this year as the infection of influenza virus has decreased in the past two years, the immunity to influenza has decreased, and the restrictions on Covid-19 have been relaxed. There is a possibility. Compared to 2021.

However, this does not necessarily mean that more cases will soon return to pre-Covid-19 levels.

Shabir Madhi, a professor of vaccines at the University of the Witwatersland, finds it difficult to predict exactly what will happen during this flu season, but “can take some lead from what’s happening in the Northern Hemisphere.” “.

He says the flu season in the United States, which is now nearing its end, is virtually less serious than the pre-pandemic season. The Centers for Disease Control and Prevention reports that 2,000 to 5,800 people died and 3.5 to 5.8 million people got the flu during the 2021 to 2022 influenza season.

This is a significant reduction from the 2019-2020 influenza season, causing 39-56 million influenza illnesses and 24,000-62,000 deaths.

Maddy says the exact reason for the significant reduction in cases and deaths in the United States is still unknown.

“Still, it may be related to restrictions on people’s movements, especially intercontinental travel. This is an important feature from a recirculation perspective,” he says.

In addition to this, Maddy states that physical distance, masking, and other interventions helped stop the flu infection.

“It’s hard to predict, but the flu season can be worse than in 2020-2021, when there was little flu, but the flu season is relatively compared to the pre-Covid flu season. I’m still optimistic when it comes to moderation, “he says. To tell.

Professor Cheryl Cohen, director of the NICD Respiratory Diseases and Meningitis Center, and Dr Sibongile Walaza, an epidemiologist at the center, responded to a written question by saying: We are monitoring specific locations in South Africa, and the influenza pandemic in 2020 and 2021 is lower than in the previous year. “

Influenza viruses are usually imported from the Northern Hemisphere and begin to spread in South Africa around May / June. However, it has subsided again and may come back around August.

“There is less travel and the chances of the influenza virus being imported into South Africa are low. As human mobility increases, the number of cases of influenza can increase,” says Mahdi.

Importance of vaccination

NICD recommends flu vaccines for people at high risk of developing severe flu illnesses and complications. Influenza vaccination is said to continue to be the primary means of preventing influenza transmission and reducing the risk of serious illness. The NICD website also advises that you should wash your hands frequently with soap and water or alcohol-based finger rubs to avoid contact with sick people to avoid getting the flu.

The groups covered by the Ministry of Health’s 2022 influenza vaccination campaign include healthcare professionals, individuals aged 65 and over, cardiovascular disease (including chronic heart disease, hypertension, stroke, and diabetes), and chronic lung disease (asthma, chronic). Individuals (including obstructive pulmonary disease). And pregnant women as well as individuals living with HIV.

Muddy says it is imperative that people with weakened immunity be vaccinated against the influenza virus as the transmission of influenza during the pandemic of Covid-19 is reduced.

South Africa has an estimated 17 million people who are considered the priority group for vaccination.

“But less than 10% of these people are actually vaccinated because there aren’t enough vaccines available and there is no culture of people to get the flu vaccine,” says Madhi.

Vaccine and influenza strain matching

“But in addition to the immune gap, it’s also very difficult to predict the characteristics of the next strain that circulates,” explains Maddy. “That’s one of the reasons why the flu vaccine used in the Northern Hemisphere has had little effect on the present, because the flu virus is a mismatch between what is circulating and what is contained in the vaccine. . “

According to Maddy, the current flu vaccine was “insufficient” in the Northern Hemisphere, where the flu season is nearing its end.

Influenza mutates frequently, and the effectiveness of influenza vaccines depends on how well they can protect against circulating viral strains. New influenza vaccines need to be created each year to reflect viral mutations and different strains around the world.

This year’s strains and vaccines

Of the influenza strains detected in South Africa, influenza A and B are the most susceptible. The influenza virus strains identified so far through the NICD influenza monitoring system were the normal seasonal influenza B strains of the Victoria and Yamagata strains and influenza A of subtypes H3N2 and H1N1.

According to Cohen and Waraza, the trivalent vaccine covers all three important types of influenza A / H1N1, A / H3N2 and B / Victoria. In addition to the target strains of the trivalent vaccine, the tetravalent vaccine also targets the B / Yamagata strain.

In 2022, trivalent vaccines will be available in the public sector and tetravalent vaccines will be available in both the private and public sectors. Vaccines are free for high-risk individuals in the public sector.

They say the updated guideline is that the Covid-19 vaccine can be given at the same visit as the influenza jab. The two vaccines require the use of the opposite arm.

How effective is the flu vaccine?

Cohen and Waraza agree with Mahdi that the performance of influenza vaccines varies each year depending on how well the strains of the vaccine match the circulating strains.

“We don’t know which strains will be prevalent this year. Vaccine performance is usually assessed after the season,” they say.

Most countries in the Northern Hemisphere are currently using 4-valent vaccines containing the H3N2 strain that dominates the flu season. The genetic drift of the strain itself determines how well the vaccine works.

“In reality, the 4-valent vaccine has had little value since the pandemic of the Yamagata strain B, which has disappeared significantly, and is now even more valuable,” said Mahdi.

He added that the inclusion of Yamagata and Victorian pedigrees in the vaccine “limited public health value” and was associated with “marketing above all” and “doubling the price of the vaccine”.

Given the experience in the Northern Hemisphere, Mahdi is “pessimistic” and the vaccine will be much more effective in South Africa this year.

“Fortunately, this year too will be offset by the relatively weakening flu season,” he says.

The effectiveness of a vaccine depends on the season and how closely the vaccine matches the strain that ultimately circulates. “It can be anything between 10% and 80%. Unfortunately, it currently sits closer to 10% than 80%,” he says.

RS virus

Meanwhile, in South Africa, respiratory syncytial virus (RSV), the most common cause of bronchiolitis and lower respiratory tract disease, has experienced the worst outbreaks in 10 years. It is highly contagious, infection with RSV does not result in permanent or long-term immunity, and reinfection can occur.

“This year was a particularly tough season. Children currently admitted to Chris Hanibala Gwanat Hospital have a 60% positive rate of RSV,” says Maddy.

So far, according to NICD, RSV was detected in 2022 in 19% (105/529) of children under the age of 5 hospitalized for lower respiratory tract disease at the sentinel pneumonia monitoring site.Details are summarized in Weekly Respiratory Pathogen Surveillance Report..

The number of RSV-positive tests in children under 5 years of age began to increase at week 5 (weeks up to February 13), with 35% (28/81) and 32% (24/74) of children admitted with LRTI. ) Continues to increase. RSV positivity will be tested at the 9th week (week until March 6th) and 10th week (week until March 13th) sentry sites, respectively.

* This article was published by Spotlight -Health journalism for the public good