The story of how vaccines save lives is important to tell – now more than ever

Only clean drinking water rivals vaccination in its ability to save lives, according to the World Health Organization (WHO). And, although vaccine safety gets more public attention than vaccination effectiveness, independent experts and the WHO have shown that vaccines are far safer than therapeutic medicines.

Vaccines have virtually eliminated devastating and cruel illnesses like polio and pertussis (whooping cough), and serious lower respiratory tract diseases.

Wits University scientists are leaders in paediatric immunisation research, with their studies informing global public health programmes. Wits teams are also leading two crucial Covid-19 vaccine trials in South Africa and Africa.

Dr Michelle Groome, Senior Researcher at the Vaccines and Infectious Diseases Analytics Research Unit (VIDA) at Wits, says that since the introduction of the rotavirus vaccine in Africa, for example, an estimated 135 000 rotavirus hospitalisations and 21 000 deaths have been prevented annually. Rotavirus causes serious diarrheal symptoms in children. South Africa was the first African country to introduce the rotavirus vaccine into its national immunisation programme in 2009, and since then, diarrhoeal hospitalisation has decreased by 34-57% for children under the age of five.

“Vaccination is the best way to prevent many childhood diseases, increase life expectancy and improve a person’s quality of life. In a low-to-middle income country, like South Africa, the robust immunisation programme is a major achievement. We have seen a decline in deaths from infectious diseases and now rely on high vaccine coverage to prevent outbreaks and disease,” says Groome.

Vaccines better protect babies of mothers from poorer countries

A vaccination against the respiratory syncytial virus (RSV) has been found to better protect infants born to women from low-to-middle income countries, such as South Africa, than those in wealthier countries.

Dr Clare Cutland, the Scientific Coordinator at the African Leadership in Vaccinology Expertise (ALIVE) consortium, and Professor Shabir Madhi, Executive Director of VIDA and the Dean of the Faculty of Health Sciences at Wits, co-authored a seminal global study on RSV. The paper, published in the New England Journal of Medicine in July 2020, provides evidence that immunising pregnant women could protect their infants from severe RSV, which is a leading cause of lower respiratory tract infection.

While the RSV vaccine will not be administered to pregnant women yet, the global study is pegged to inform WHO policy on the use of this initiative in public immunisation programmes.

Vaccine reinvention for Covid-19

The Wits Reproductive Health and HIV Institute (Wits RHI) is part of a global network of researchers, known as the Crown Collaborative, conducting the ‘Crown Coronation’ trial, which aims to determine whether the measles, mumps and rubella (MMR) vaccine given to healthcare workers reduces Covid-19 symptoms. Dr Sinéad Delany-Moretlwe and Professor Bruce Biccard from the Wits RHI are the national principal investigators.

“In places where the MMR vaccine uptake is high, there seems to be lower incidences of severe Covid-19. This is really exciting for us, because it means we can use an already tested vaccine and safely repurpose it, at a low cost,” said Delany-Moretlwe.

Wits-led Covid-19 vaccine trials

Wits University is currently involved in two Covid-19 vaccine trials, both led by Madhi.

The Oxford Covid-19 vaccine trial, announced in June 2020, is the first clinical trial for the Covid-19 vaccine in South Africa and Africa. The ChAdOx1 nCov-19 vaccine has been described by the WHO as amongst the world’s leading candidates. Moreover, a vaccine developed in Africa is a huge achievement for promoting context-specific treatment, and to generate evidence about how a Covid-19 vaccine will work in low-to-middle income countries.

The Novavax Covid-19 vaccine trial is a partnership between VIDA and Maryland-based bio-technology company, Novavax. The Novavax Covid-19 vaccine, known as NVX-CoV2373 contains a nanoparticle S-protein. The trial will determine whether it protects against the disease in adults aged older than 18 years.

Vaccines and herd immunity

South Africa bucked global Covid-19 trends, with significantly fewer deaths in relation to the number of people likely to have been infected with the virus.

Scientists could not have predicted that about one-third of the population would be infected with the virus nor that the country would have a declining transmission rate. One reason may be herd immunity – which is a form of indirect protection from infectious disease that occurs when a sufficient percentage of a population has become immune to an infection, whether through previous infections or vaccination.

Non-pharmaceutical interventions like wearing face masks, social distancing and avoiding crowds played a major role.

“We don’t know, however, if immunity is long lasting. We can’t just say that because one-third of South Africans may have contracted the virus that we have sustainable ‘herd immunity’,” says Madhi. “Our unique situation [lower deaths despite greater numbers of infections] could be explained by many factors. We will always need a vaccine to protect us against a serious illness like Covid-19.”

Vaccines and herd immunity

A vaccine is a biological product that elicits an immune response against a specific bacteria or virus.

The immune response stimulates lymphocytes (white blood cells) in the body to produce antibodies and other inflammatory responses to kill off, inactivate or neutralise the germ when a person is exposed or infected.

The antibody response is generally specific to individual germs, hence the need for different types of vaccines.

Immunisation is the process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine.

How is a vaccine made?

One way is by using either a weakened or attenuated (reduced) version of the germ, for example oral polio virus, that has limited ability to replicate or cause illness.

Another approach is to use an inactivated version of the targeted vaccine, for example, the pertussis (whooping cough) vaccine.

More common approaches include using only a specific target (antigen) of the germ, which can also target the immune response to neutralise the germ. These antigens are sometimes coupled with another chemical compound, an ‘adjuvant’, to enable a more robust immune response.

Newer technologies include using weakened viruses that cause mild or no illness, and that are engineered, or technology that involves directly injecting the genetic material (messenger RNA or DNA) that codes for the antigen.

Source : Wits University – How vaccines save lives
Author : Beth Amato