A mandatory vaccine newborns receive to fight off tuberculosis (TB) may also have a positive impact on the COVID-19 curve. A new study suggests that there is a correlation between the Bacille Calmette-Guérin (BCG) vaccine and a flattened curve of coronavirus infection.
South Africa is one of many countries where the BCG vaccine is mandatory for newborns, and has been for decades. Countries like the United States, Italy and Lebanon have never mandated the vaccine, and others like Australia, Spain, and Ecuador ended their mandatory policy when TB ceased to be a threat.
The vaccine is about 100 years old, and was created at the Pasteur Institute in France. It is one of the longest standing vaccines in the world. While this vaccine is mainly used to protect children against TB, it can also be used to fight other respiratory tract infections in kids and adults.
Earlier in the year, epidemiologists cautioned against believing the vaccine would impact on the rate of infection as it was too early to tell.
An initial study in March suggested there is a link between the vaccine and the COVID-19 curve, but was discredited as it was not peer-reviewed and took place before the majority of countries saw a surge in cases. There were also a number of potential biases not considered in the study.
A new report recently published in Science Advances considers a variety of biases previous studies did not, and suggests there is a connection.
The study is headed by scientist Dr. Martha Berg from the University of Michigan, and posits that because the BCG vaccine has been shown to offer a long-lasting protective effect not only against TB but also against various other infectious diseases, it could help protect against coronavirus.
The researchers analysed countries where the vaccine is and has been mandatory since at least the year 2000 to those where it is not. They also considered the rate of the day-by-day increase in both confirmed cases (134 countries) and deaths (135 countries) in the first 30-day period of country-wide outbreaks.
They also controlled for variables such as per capita GDP and cultural differences in an effort to eliminate biases.
Results showed that there was a substantial association between BCG vaccination and flattening the curve in the spread of COVID-19. One of the models estimates that the total number of COVID-19–related deaths in the United States as of March 29, 2020 would have been 468, which is 19% of the actual figure of 2467, if the United States had instituted the mandatory BCG vaccination several decades earlier.
Researchers also note that the growth curves were as steep in countries that stopped mandatory vaccines before 2000 as in those that never mandated the vaccine.
“BCG vaccination may become effective only when a substantial proportion of the population is made resistant to a virus. That is to say, the spread of the virus may be slowed only when there is herd immunity that prevents the virus from spreading easily across the population,” they write.
“Linear mixed models revealed a significant effect of mandated BCG policies on the growth rate of both cases and deaths after controlling for median age, gross domestic product per capita, population density, population size, net migration rate, and various cultural dimensions (e.g., individualism). Our analysis suggests that mandated BCG vaccination can be effective in the fight against COVID-19,” reads the paper.
Epidemiologists assert that while the vaccine may have an impact on flattening the curve, it has not been shown to affect how the virus spreads like wildfire.
The BCG vaccine was first introduced to South Africa in the 1950s but was sporadic and only given to some school-going children at the time, Prof Greg Hussey, who leads Vaccines for Africa at the University of Cape Town (UCT) tells Sowetan Live. It was only in 1973 that the vaccine was distributed with high coverage to newborns across the country.
This means that people born from 1973 and onwards have received the vaccine or are more likely to have received the vaccine. Those in their 50s and above are much less likely to have received the vaccine, and thus might not have ‘herd immunity’.
In May 2020, a vaccine trial began at Tygerberg Hospital in Cape Town to test whether the BCG vaccine can reduce the probability of coronavirus and limit the severity of its symptoms. Similar trials are being conducted in Norway and the Netherlands.