Does this mean you can make your way through the world like the old days without fear of spreading the virus? Deborah Fuller is a microbiologist at the University of Washington School of Medicine working on coronavirus vaccines. She explains what the science shows about transmission post-vaccination – and whether new variants could change this equation.
1. Does vaccination completely prevent infection?
The short answer is no. You can still get infected after you've been vaccinated. But your chances of getting seriously ill are almost zero.
Many people think vaccines work like a shield, blocking a virus from infecting cells altogether. But in most cases, a person who gets vaccinated is protected from disease, not necessarily infection.
Every person's immune system is a little different, so when a vaccine is 95% effective, that just means 95% of people who receive the vaccine won't get sick. These people could be completely protected from infection, or they could be getting infected but remain asymptomatic because their immune system eliminates the virus very quickly. The remaining 5% of vaccinated people can become infected and get sick, but are extremely unlikely to be hospitalized.
Vaccination doesn't 100% prevent you from getting infected, but in all cases it gives your immune system a huge leg up on the coronavirus. Whatever your outcome – whether complete protection from infection or some level of disease – you will be better off after encountering the virus than if you hadn't been vaccinated.
Vaccines prevent disease, not infection. (National Institute of Allergy and Infectious Diseases, CC BY)
2. Does infection always mean transmission?
Transmission happens when enough viral particles from an infected person get into the body of an uninfected person. In theory, anyone infected with the coronavirus could potentially transmit it. But a vaccine will reduce the chance of this happening.
In general, if vaccination doesn't completely prevent infection, it will significantly reduce the amount of virus coming out of your nose and mouth – a process called shedding – and shorten the time that you shed the virus. This is a big deal. A person who sheds less virus is less likely to transmit it to someone else.
This seems to be the case with coronavirus vaccines. In a recent preprint study which has yet to be peer reviewed, Israeli researchers tested 2,897 vaccinated people for signs of coronavirus infection. Most had no detectable virus, but people who were infected had one-quarter the amount of virus in their bodies as unvaccinated people tested at similar times post-infection.
Less coronavirus virus means less chance of spreading it, and if the amount of virus in your body is low enough, the probability of transmitting it may reach almost zero. However, researchers don't yet know where that cutoff is for the coronavirus, and since the vaccines don't provide 100% protection from infection, the Centers for Disease Control and Prevention recommends that people continue to wear masks and social distance even after they've been vaccinated.
3. What about the new coronavirus variants?
New variants of coronavirus have emerged in recent months, and recent studies show that vaccines are less effective against certain ones, like the B1351 variant first identified in South Africa.
Every time SARS-CoV-2 replicates, it gets new mutations. In recent months, researchers have found new variants that are more infective – meaning a person needs to breathe in less virus to become infected – and other variants that are more transmissible - meaning they increase the amount of virus a person sheds. And researchers have also found at least one new variant that seems to be better at evading the immune system, according to early data.
So how does this relate to vaccines and transmission?
For the South Africa variant, vaccines still provide greater than 85% protection from getting severely ill with COVID–19. But when you count mild and moderate cases, they provide, at best, only about 50%-60% protection. That means at least 40% of vaccinated people will still have a strong enough infection – and enough virus in their body – to cause at least moderate disease.
If vaccinated people have more virus in their bodies and it takes less of that virus to infect another person, there will be higher probability a vaccinated person could transmit these new strains of the coronavirus.
If all goes well, vaccines will very soon reduce the rate of severe disease and death worldwide. To be sure, any vaccine that reduces disease severity is also, at the population level, reducing the amount of virus being shed overall. But because of the emergence of new variants, vaccinated people still have the potential to shed and spread the coronavirus to other people, vaccinated or otherwise. This means it will likely take much longer for vaccines to reduce transmission and for populations to reach herd immunity than if these new variants had never emerged. Exactly how long that will take is a balance between how effective vaccines are against emerging strains and how transmissible and infectious these new strains are.
Deborah Fuller, Professor of Microbiology, School of Medicine, University of Washington
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Women across the world have made an enormous contribution to the global efforts to tackle COVID-19. Not only do women make up 70% of the world's health workers and first responders, women in STEM fields have been leading research into the virus, creating trackers and developing vaccines.
But the pandemic has had a disproportionate social and economic impact on women, as many have borne the brunt of childcare duties or lost jobs in sectors most affected – and this includes women scientists.
February 11th is UN International Day of Women and Girls in Science – and the theme this year is celebrating the women scientists at the forefront of the fight against COVID-19, including Dr Özlem Türeci, co-founder of BioNTech, which helped produce the first vaccine.
Women represent almost half the students at Bachelor's (45%), Master's (55%) and PhD (44%) levels of study, according to UNESCO's forthcoming Science Report – but only 33% of the world's researchers are women.
To encourage more girls and women to take up careers in the STEM fields, UNESCO is gathering some of the world's leading COVID-19 experts for a virtual event.
"We need science, and science needs women. This is not only about making a commitment to equal rights; it is also about making science more open, diverse and efficient," said Phumzile Mlambo-Ngcuka, Executive Director of UN Women, and Audrey Azoulay, Director-General of UNESCO.
Here are just some of the women in STEM around the globe who have been making a difference during the pandemic.
Dr Özlem Türeci
Dr Türeci and her husband Dr Ugur Sahin co-founded biotechnology company BioNTech in Germany in 2008. In 2020, BioNTech and pharmaceutical firm Pfizer developed the first approved RNA-based vaccine against COVID-19. They celebrated the news that it had 90% efficacy with a cup of Turkish tea, the pair told The New York Times. Recently featured on the cover of Time magazine, the scientists plan to produce two billion doses of the vaccine this year to help bring the pandemic to an end.
Dr Soumya Swaminathan
A paediatrician and one of India's leading public health experts, known for her groundbreaking research on tuberculosis, Dr Swaminathan was appointed the World Health Organization's (WHO) Chief Scientist in 2019 and has been coordinating international work on vaccine development. She spoke about challenges women researchers face at the Women Leaders in Global Health Conference 2020: "It is more difficult for women researchers to get their grants approved … and women also have difficulties in getting their results published, if you are from developing countries, in journals, because of perceived biases. I have faced those kinds of challenges and biases."
Ramida Juengpaisal
Within a night in March 2020, Ramida Juengpaisal and her colleagues at web design firm 5LAB in Bangkok, Thailand, built a tracker of COVID-19 cases, giving the city's eight million residents up-to-date news and information about the pandemic and helping to stop the spread of misinformation. She told Reuters the perception that girls are less suited to technology-based roles is gradually shifting: "We need more women in tech. One good thing about this crisis is that we have seen people – including women – come forward to create things that are useful to others, and be recognized."
Ramida Juengpaisal built a COVID-19 tracker for Bangkok – overnight. Image: UN Women/Stefan Abrecht/BioNTechProfessor Sarah Gilbert
Prof Gilbert is the Oxford Project Lead for the Oxford/AstraZeneca vaccine, now recommended for use by all adults worldwide by the WHO. When the genetic sequence for the new coronavirus was published in January last year, she swiftly built on her work developing a vaccine for MERS, which used chimp adenovirus to deliver the spike protein into humans. Prof Gilbert is currently working on a new version of the vaccine to tackle the South African variant.
Somaya Faruqi
Faruqi and her all-female robotics team began developing a low-cost, lightweight ventilator using locally available, second-hand car parts, after the first COVID-19 case was reported in her home province of Herat in Afghanistan. She told UN Women: "Sometimes, families think science and tech are male fields and prefer that their girls don't enter them. We have less role models for young women in these fields, and that makes it more challenging for young women to enter this industry."
Neema Kaseje
Kaseje is the Founder of Surgical Systems Research Group in Kenya, which seeks to rapidly expand access to health services by leveraging youth, technology and community health workers. Since May 2020, the group has helped to flatten the curve of COVID-19 cases in Siaya County, by combining digital tools and data science with the work of young people and community health workers to raise awareness about preventative measures.
Professor Devi Sridhar
American public health researcher Prof Sridhar is a leading authority on COVID-19 in the UK and Professor and Chair of Global Public Health at Edinburgh University. She is known for her work on assessing the international response to the Ebola virus epidemic in West Africa. Among her frequent media appearances, she spoke to the World Economic Forum's World Vs Virus podcast about why ethnic minorities in Europe and North America were at greater risk from COVID-19.
Dr Anggia Prasetyoputri
Dr Prasetyoputri was awarded the 2020 L'Oréal-UNESCO National Fellowship For Women in Science (FWIS) by L'Oréal Indonesia for her research on bacterial coinfections in COVID-19 patients using swab sample sequencing. COVID-19 patients whose immune systems are already weakened by the virus, are more susceptible to other viruses and bacteria. So Dr Prasetyoputri worked out a quick and simple way to identify these coinfections – and help doctors prescribe the right treatment.
Reprinted with permission of the World Economic Forum. Read the original article.
