How do COVID-19 vaccines work?

 COVID-19 vaccines work by introducing the immune system to an inactivated form of the SARS-CoV-2 coronavirus or a part of it. This does not cause COVID-19 but equips the body to fight against future infection with the virus.

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub and follow our live updates page for the most recent information on the COVID-19 pandemic.

All vaccines work by training the immune system to respond to future infection. Vaccines are overwhelmingly safe for the majority of people who receive them, and they do not cause disease.

There are 12 vaccines against COVID-19 that have authorization for use in various locations around the world.

Vaccine developers worked under unprecedented conditions to develop vaccines against COVID-19 after the emergence of the SARS-CoV-2 virus in late 2019. It took less than a year for the first COVID-19 vaccines to gain authorization for use.

While this is significantly faster than for all other vaccines, developers leveraged existing vaccine technology and a concerted global effort — working alongside health authorities such as the Food and Drug Administration (FDA) — to work at this pace.

In this Special Feature, we take a look at how different COVID-19 vaccines work and what scientists mean when they talk about side effects and vaccine efficacy.

Specifically, we cover:

• mRNA vaccines
• viral vector vaccines
• subunit vaccines
• inactivated vaccines
• vaccine side effects
• vaccine efficacy

Different vaccine types

Although all of the COVID-19 vaccines in use around the world aim to achieve the same goal — namely, protection from COVID-19 — they employ different vaccine technologies.

Some vaccines are based on the whole SARS-CoV-2 virus, others use only parts of it, and some do not use any material derived directly from the virus.

The sections below provide an overview of the different types of COVID-19 vaccines that have authorization for use in at least one country.

mRNA vaccines

The COVID-19 mRNA vaccines that BioNTech-Pfizer and Moderna developed are the first mRNA vaccines authorized for use in humans outside of clinical trials. However, the technology is not new.

Scientists have been working on mRNA vaccine candidates for infectious diseases and cancer for a number of years.

mRNA vaccines do not contain any part of the SARS-CoV-2 virus. Instead, they carry a chemically synthesized piece of messenger (m)RNA that contains the information necessary for our own cells to make the SARS-CoV-2 spike protein.

Our cells make this protein and present it to our immune system, which responds by creating antibodies and developing longer lasting immunity in the form of T cell and B cell responses.

It is not possible to develop COVID-19 from an mRNA vaccine because it does not carry the instructions necessary to make the entire coronavirus.

Source: Medical News Today

How does the Sputnik V COVID-19 vaccine work?

 The Sputnik V COVID-19 vaccine uses two harmless viruses that deliver the genetic code for our cells to make a protein from the new coronavirus. This trains our immune system to fight against future infections with the new coronavirus.

The Sputnik V vaccine, which also bears the name Gam-COVID-Vac, currently has authorization for use in 68 countries. The Gamaleya National Center of Epidemiology and Microbiology in Moscow, Russia, developed the vaccine.

Sputnik V is a viral vector vaccine designed to produce lasting immunity against COVID-19. According to an interim analysis of phase 3 clinical trial data published in The Lancet, the vaccine’s efficacy is 91.6%Trusted Source.

However, a number of scientists have publicly called into question the results from the phase 1/2Trusted Source and phase 3Trusted Source trials.

What is a viral vector? 

A viral vector is a harmless virus that can deliver a gene to our cells that they turn into a protein. Scientists have studied the use of viral vectors for gene therapy and vaccines.

When a viral vector vaccine delivers the genetic code for our cells to make a pathogen’s protein, our immune system reacts to the presence of the protein and the viral vector. This elicits an immune response that can lead to lasting immunity.

The Sputnik V COVID-19 vaccine uses two different adenoviruses as the viral vectors. Adenoviruses are a large family of viruses that can cause the common cold.

In order to train the immune system to recognize the SARS-CoV-2 virus, which causes COVID-19, people receive the vaccine in two doses at an interval of 21 days. The first shot contains adenovirus 26 (Ad26) as the viral vector, while the second shot contains adenovirus 5 (Ad5). Both shots also contain the gene for the SARS-CoV-2 spike protein.

Scientists have chemically modified the adenoviruses in the Sputnik V COVID-19 vaccine to stop them from replicating. This means that the viral vectors cannot cause an adenovirus infection.

The vaccine also cannot cause COVID-19 because it does not contain the entire SARS-CoV-2 virus.

Our immune system reacts to the vaccine by developing antibodies specific to the SARS-CoV-2 virus and by eliciting T-cell responses. In the event of future infection, our bodies can rapidly produce these antibodies to bind to the virus and prevent it from entering our cells.

T-cells can kill infected cells. Both the viral vector and the SARS-CoV-2 spike protein play a role in building up immunity in this way.

Source: Medical News Today

Does being part of a larger family raise cardiovascular risk?

 

• A recent study investigated the association between the number and relative age of siblings and the combined risk of fatal and nonfatal cardiovascular events.
• The results suggest that being part of a larger family with multiple siblings or being a second- or third-born sibling could increase the risk of cardiovascular events.
• This is the first study involving birth order and family size that also includes the risk of nonfatal cardiovascular events.

According to the World Health OrganizationTrusted Source, cardiovascular diseases (CVD), which affect the heart and blood vessels, are the leading cause of death globally.

Family history and lifestyle factors such as smoking and an unhealthy diet are well-established risk factors for cardiovascular diseases, including coronary heart disease and stroke.

Besides a family history of CVD largely influenced by genetic predisposition, there is also evidence to show that family structure, especially birth order but not family size, can influence the risk of death due to cardiovascular conditions.

However, only a few studies have looked at the impact of family structure on nonfatal cardiovascular events.

A comprehensive understanding of the impact of family structure on CVD risk requires the inclusion of both fatal and nonfatal cardiovascular events.

A large observational study involving people aged 30–58 years at onset now shows that the number of siblings and birth order can influence the risk of total cardiovascular events over a 25-year follow-up period.

A team of researchers led by Prof. Peter Nilsson at Lund University in Sweden conducted this study. Their findings appear in the journal BMJ Open.

Linking family structure to cardiovascular risk

To obtain information about family structure, the researchers used the Swedish Multi-Generation Register (MGR)Trusted Source. The register includes records of biological parents of more than 95% of the population born after 1931 and alive in 1961, thus providing an exceptionally large dataset.

The study included data from 1.36 million men and 1.32 million women aged 30–58 years in 1990. They determined the risk of nonfatal and fatal cardiovascular events as well as total mortality among these individuals using data from death and hospital discharge registers between 1990 and 2015.

Factors such as socioeconomic status, education level, marital status, and medical conditions such as diabetes can influence CVD risk.

The team adjusted their analysis to account for the influence of these variables and isolate the impact of family structure on cardiovascular events.

Potential impact of family structure

In terms of family size, men and women with more than one sibling were at a lower risk of death than those with no siblings.

Men with one or two siblings had a lower risk of cardiovascular events than those with no siblings, while those with four or more siblings had a higher risk.

Men with three or more siblings also had a higher risk of coronary events compared with no siblings.

Similarly, compared with women with no siblings, women with three or more siblings had a higher risk of cardiovascular events. In addition, women with two or more siblings had a higher risk of coronary events.

In the case of birth order, first-born individuals had a lower risk of cardiovascular and coronary events than those who were born later.

In contrast, first-born individuals had a higher risk of overall mortality than second-born siblings.

The researchers point out that “more research is needed to understand the links between sibling number and rank with health outcomes.”

Implications for public health policy

While the study’s strengths included a large sample size and comprehensive data on family structure and hospital records, it also had some limitations.

The researchers note that the study, owing to its observational design, only shows a correlation between family structure and cardiovascular events and does not establish causation.

Due to the lack of data, the researchers were also unable to account for variables such as diagnostic procedures, parental socioeconomic status, smoking, diet, and other lifestyle factors that could have influenced their analysis of CVD risk.

Since social factors are likely to contribute to the impact of family structure on health outcomes, including cardiovascular risk, the study’s results could influence public health policy.

Significantly, this study was conducted in Sweden, which has a generous welfare system. The authors observe that “this is of public health interest as different countries endorse different policies to support families and number of children.”

“Future research should be directed to find biological or social mechanisms linking the status of being first born to lower risk of CVD, as indicated by our observational findings,” state the authors.

Source: Medical News Today

Diabetes care falls short for most of the world's population

 

• A study of diabetes treatment in 55 low and middle income countries found that many of the participants with diabetes were unaware that they had the condition.
• Overall, less than 5% were getting adequate drug treatments and lifestyle advice.
• The researchers pooled data from nationally representative surveys that asked people what treatments they were taking to reduce blood sugar, blood pressure, and cholesterol levels and what advice they had received about diet, exercise, and weight.
• Diabetes medications are cheap and proven to reduce both the risk of diabetes-associated complications and the long-term costs of care.

The International Diabetes Federation notes that of the estimated 463 million adults in the world who have diabetes, almost 80% live in low and middle income countries.

DiabetesTrusted Source increases a person’s risk of a range of disabling and potentially fatal complications, including heart attack, stroke, blindness, and damage to the kidneys and nerves.

Drug treatments for the condition are cheap and proven to reduce morbidity and mortality.

However, the ability of health services in low and middle income countries to diagnose the condition and deliver these treatments is often limited. This inevitably leads to unnecessary suffering and many avoidable deaths.

Doctors at the University of Michigan in Ann Arbor and Brigham and Women’s Hospital in Boston, MA, recently led a study to estimate the scale of the problem.

The researchers drew on data from standardized household surveys in low and middle income countries that included information on blood test results for diabetes and self-reported treatments.

They discovered that only 4.6% of people with diabetes were receiving the whole package of care that the World Health Organization (WHO)Trusted Source recommends for treating the condition in primary care.

While 50.5% and 41.3% of the respondents were taking drugs to lower their blood sugar and blood pressure, respectively, only 6.3% were on cholesterol-lowering medication.

Overall, 32.2% of respondents said that they had received advice on diet. Just 31.5% had received advice on weight loss, and 28.2% on exercise.

“Diabetes continues to explode everywhere, in every country, and 80% of people with it live in these low and middle income countries,” says lead author David Flood, M.D., M.Sc., who is a national clinician scholar at the University of Michigan Institute for Healthcare Policy & Innovation.

“It confers a high risk of complications, including heart attacks, blindness, and strokes,” he adds. “We can prevent these complications with comprehensive diabetes treatment, and we need to make sure people around the world can access treatment.”

The research has been published in The Lancet Health LongevityTrusted Source.

Lack of treatment for high cholesterol

The household surveys provided data for a total of 680,102 adults in 55 low and middle income countries.

Blood tests indicated that 37,094 of these individuals had diabetes. However, only 43.9% of them said that they had received a diagnosis.

Even among those with a formal diagnosis, there was room for improvement in terms of drug treatments. While 85% and 57% of those who knew that they had diabetes were taking drugs to lower their blood sugar levels and blood pressure, respectively, only 9% were taking a statin to lower their cholesterol.

Countries with higher incomes tended to have better coverage across all the diabetes treatments.

Coverage was generally highest in Latin America and the Caribbean and lowest in Oceania (Pacific islands) and sub-Saharan Africa.

The researchers have passed their findings to the WHO, which launched the Global Diabetes CompactTrusted Source on April 14, 2021, to step up efforts to prevent and treat diabetes worldwide.

Two-way links with COVID-19

People with diabetes and obesity are more likelyTrusted Source to develop severe COVID-19 infections, and researchers also believe that COVID-19 may trigger diabetes.

Jennifer Manne-Goehler, M.D., Sc.D., one of the authors of the new paper, told MNT that the pandemic has increased the urgency to improve diabetes services in resource-limited contexts.

Dr. Manne-Goehler is an infectious diseases physician at Brigham and Women’s Hospital and a clinical fellow at Harvard Medical School, both in Boston, MA.

She and her colleagues have found that diabetes is associated with “poor early outcomesTrusted Source” for people hospitalized with COVID-19.

“The COVID-19 pandemic has really highlighted how important the intersection between diabetes and infectious conditions is and the far-reaching implications of ensuring everyone with diabetes has access to much needed services,” she said.

Limitations of the research

The study authors highlight several limitations in their paper, including inconsistencies across the different surveys in terms of the year they took place, the diagnostic tests that were used, and the age profile of the participants.

These differences and others may account for some of the observed variation in treatment coverage among countries.

The researchers also report that they were unable to get enough data about the availability of counseling to quit smoking.

They write that this is a limitation because smoking is a major contributor to the risk of cardiovascular disease among people with diabetes.

Source: Medical News Today

Dairy milk may lower cholesterol and reduce coronary heart disease risk

 

• A new study suggests that drinking dairy milk may lower cholesterol levels.
• The study consists of a meta-analysis of three surveys involving over 400,000 individuals.
• The scientists found that even though drinking milk leads to higher body mass index (BMI) and body fat, it still lowers the risk of coronary heart disease.

Dairy milk is a complex substance. For example, it contains 18 out of 20Trusted Source essential proteins and amino acidsTrusted Source, but it also contains saturated fats.

Perhaps this is why attempts to definitively identify its role in cardiometabolic diseases and its effect on cholesterol levels have produced conflicting results.

A newly published study from the University of Reading in the United Kingdom attempts to resolve such contradictions. The study is based on a meta-analysis of three existing large population studies.

The authors conclude that people who consume dairy milk have lower levels of both types of cholesterol and a lower risk of coronary heart disease than people who do not drink milk.

Despite this, people who do drink milk have higher BMI and more body fat. These are typically considered risk factors for cardiovascular issues.

The study was a collaboration involving researchers from the University of Reading, the University of South Australia in Adelaide, the Southern Australian Health and Medical Research Institute, also in Adelaide, University College London in the U.K., and the University of Auckland in New Zealand.

The results appear in the International Journal of ObesityTrusted Source.

A genetic approach

The study authors note that the contradictory results of earlier studies may have to do with unknown confounding factors, or confounders that studies have not measured well enough. For example, people who drink milk may also eat more butter and smoke more, raising their cholesterol and heart disease risk.

If researchers do not take these confounders into account, they may identify an association between milk intake and high cholesterol and heart disease risk that might not exist.

Another problem with earlier studies is reverse causation. People who are overweight often receive advice to reduce their dairy product intake. If scientists carry out a study without knowing when those people reduced their intake, the analysis could suggest that the excess weight was due to a low rather than a high dairy product intake.

One approach that scientists can take to overcome this issue is to use information about genetic variation. These studies are called Mendelian randomization studiesTrusted Source.

Since genetic variations originate at conception, reverse causation cannot influence them. Furthermore, they should not affect the tendency of someone to undertake a genetically unrelated behavior or show a raised physiological variable that is unconnected.

For example, a genetic variation that makes milk consumption more likely will not directly influence how much cholesterol someone has in their blood, as other genes control that factor. Therefore, if people with the variant drink milk and have higher or lower cholesterol, we can infer that it is the milk that influenced the cholesterol rather than some other variable.

This is exactly what the researchers behind this new study did. They leveraged a strong association between the lactase persistenceTrusted Source genotype variation and people who drink milk. They then confirmed this link using data from the GWAS catalog and found no other association with the lactase persistent variant other than increased obesity.

Therefore, for the purposes of the current study, the researchers identified the people who drink milk as those with the gene variation.

Medical News Today asked Dr. Edo Paz, of K Health, to comment on this approach. He said that such studies “may minimize biases that we typically see in observational studies, although confounding factors that affect the relationship between milk consumption and disease may still be present.”

Data for hundreds of thousands of people

The researchers performed their meta-analysis on data collected for three large studies: the 1958 British Birth cohortTrusted Source, the Health and Retirement Study, and the UK Biobank. Altogether, they included data for 417,236 individuals in their research.

The study authors conclude that people with the gene variant had lower levels of low-density lipoprotein, total, and high-density lipoprotein cholesterol.

The researchers suggest four possible explanations for this:

• The calcium and lactose in milk may enhance calcium absorption, which reduces cholesterol levels.
• People who drink milk may be consuming less fat than people who do not drink milk, a category that includes lactose-intolerant people who can, nonetheless, consume higher fat cheese and butter.
• The calcium in milk may increase the excretion of bile acids. These acids derive from cholesterol in the liver, so if excretion increases, cholesterol concentrations may eventually drop.
• Gut microbial fermentation of indigestible carbohydrates might alter and lower cholesterol synthesis.

The study also finds that people who drink milk have a 14% lower risk of developing coronary heart disease.

Prof. Karani says:

“The study certainly shows that milk consumption is not a significant issue for cardiovascular disease risk even though there was a small rise in BMI and body fat among milk drinkers. What we do note in the study is that it remains unclear whether it is the fat content in dairy products that is contributing to the lower cholesterol levels or an unknown ‘milk factor.’”

In the data from the UK Biobank, people who drink milk had an 11% lower risk of developing type 2 diabetes, though the researchers were not convinced of a genuine link between this behavior and developing diabetes or its symptoms.

As for the takeaway from the study, Dr. Paz told MNT, “I would continue to follow the recommendation from the American Heart Association, which suggests that adults eat 2–3 servings of fat-free or low fat dairy products per day.”

Source: Medical News Today

Genetic atlas reveals microbial fingerprints of the world’s cities

 

• A global survey has identified the bacteria, viruses, and archaea that live in the mass transit systems of 60 major cities.
• Each city has a distinct mix of microorganisms, which its unique climate and geography determine.
• The survey reveals that bacterial genes conferring resistance to antibiotics are widespread in the urban environment.
• Allied with microbial data from farms and sewage, the atlas could provide an early warning system for the spread of antimicrobial resistance and outbreaks of infectious disease.

“If you gave me your shoe, I could tell you with about 90% accuracy the city in the world from which you came,” says Christopher Mason, Ph.D., a professor at Weill Cornell Medicine in New York, NY.

Prof. Mason and collaborators around the world swabbed railings, seats, and ticket kiosks on bus networks and subways in 60 cities.

Over 3 years, the scientists collected 4,728 samples and sent them to a lab at Weill Cornell Medicine for analysis.

The lab used a technique called shotgun metagenomic sequencingTrusted Source to identify 4,246 known species of urban microorganisms from their DNA.

They also found 10,928 viruses, 1,302 bacteria, and two archaea that were unknown to science.

They discovered that each city has a unique microbial fingerprint, likely as a result of differences in climate and geography. In addition, there was a “core” set of 31 species that are not found in the human body but cropped up in 97% of all the samples.

The scientists have published their findings — which they describe as the “first systematic, worldwide catalog of the urban microbial ecosystem” — in the journal Cell.

They write that every day, billions of the people who live in cities come into contact with surfaces in mass transit systems, such as subways and bus networks.

Travelers bring with them the harmless “commensal” microbes that live in and on their bodies and come into contact with the organisms already in the environment.

This allowed the scientists to use the collective microbial genome or “microbiome” of mass transit systems as a proxy for the urban microbiome as a whole.

Swabbing the subway

Prof. Mason started collecting and analyzing microbial samples from the New York City subway in 2013.

When he published his initial findings, researchers from all over the world began to contact him, asking for advice about surveying their own cities.

Prof. Mason developed a protocol to standardize the sampling so that, for example, each survey included swabs from benches, handrails, and the counters of ticket booths — places where travelers either sit or put their hands.

“[T]hese are the most ‘high touch’ surfaces in most cities, and we wanted to also have locations that would be uniform across the sampled cities,” Prof. Mason explained to MNT in an email.

The latest study revealed that many different bacterial genes that confer resistance to common antibiotics are widespread in the urban environment.

The most common resistance genes that the researchers identified allow bacteria to survive exposure to two major classes of antibiotics, known as MLS and beta-lactam antiobiotics.

Healthcare professionals use these antimicrobials to treat respiratory, sexually transmitted, and skin diseases, among many other infections.

Global monitoring network

In 2015, Prof. Mason co-founded the international Metagenomics and Metadesign of Subways and Urban Biomes (MetaSUB) consortium, which incorporates samples from air, water, and sewage, in addition to hard surfaces.

He and his co-authors envisage a “global sentinel monitoring network” to track antimicrobial resistance and the spread of infectious organisms. This would incorporate microbial data from livestock and farms, for example, and sewage from cities.

They believe that the COVID-19 pandemic has thrown the need for global microbial surveillance into sharp relief.

MNT asked Prof. Mason whether his study provided a blueprint for how such an international system might work and whether he thought that there was now the political will for it.

“Yes indeed — and it could work within cities and countries and then feed these data to WHO [the World Health Organization],” he said. “This paper is a good example of how such a system could work, and we’ve also made a site that lets you browse the data.”

One important limitation of the current study was that it only sequenced DNA. Future projects will also sequence RNA, which is the genetic material of many important viruses, such as SARS-CoV-2, which causes COVID-19.

Urban biodiversity resource

In addition to helping track infections and microbial resistance, the urban microbiome could prove to be a valuable resource for new therapies.

Genetic sequence data from the current project contained more than 800,000 CRISPR arrays of which researchers were previously unaware. CRISPR arrays are DNA sequences that bacteria use to detect and destroy the viruses that prey on them.

Geneticists can use the arrays to create tools to edit genes, which could one day lead to treatments for inherited diseases.

The project also turned up novel antimicrobial compounds.

Source: Medical News Today

In Conversation: Treating cancer with mRNA vaccines

 Neuro-oncologist Dr. Santosh Kesari talks about the difficulties of treating brain cancer and the promise that mRNA vaccines hold.

Around 40% of us are likely to develop cancer at some point in our lives. Modern medicine has seen considerable advances in cancer treatments, which has contributed to a steady decline in cancer deaths in the United States over the past 30 years.

Despite this, around 10 millionTrusted Source people worldwide die each year from cancer.

Brain cancers are notoriously difficult to treat, in part because of the challenges of delivering drugs into the brain. Only around 36% of people with malignant brain cancer survive more than 5 years.

Could mRNA vaccines hold the answer?

To find out, I spoke to Dr. Santosh Kesari, a neurologist and neuro-oncologist. Dr. Kesari is the director of Neuro-oncology at Pacific Neuroscience Institute and a professor in the Department of Translational Neurosciences and Neurotherapeutics at Saint John’s Cancer Institute, both in Santa Monica, CA.

We talked about the challenges of treating brain cancer and why Dr. Kesari thinks that mRNA vaccines have the potential to impact cancer treatment on a global scale.

To hear more about how cancer develops, how experts are developing tailored treatments for individual patients, and how Dr. Kesari sees mRNA vaccines and the future of cancer therapies, listen to the accompanying podcast here.

Getting into the brain

To start our conversation, I asked Dr. Kesari to share the biggest challenge he faces when treating his patients.

“One of the difficult things and the reason we haven’t made as much progress in brain cancer, and actually all brain disorders in general, is the blood-brain barrier,” he explained.

The blood-brain barrier comprises a lining of cells around the blood vessels in the brain. It prevents big molecules and pathogens from entering the brain.

“It’s really an evolutionary protective mechanism. We don’t want all the things that the rest of our body sees to go into the brain and cause neurological problems, including infections [by] viruses, bacteria, etc.,” Dr. Kesari said.

Yet, this also means delivering drugs into the brain is difficult.

The advantages of mRNA vaccines

Messenger RNA (mRNA) vaccine technology has become almost a household name in the past year. Two COVID-19 vaccines, by Pfizer-BioNTech and Moderna, employ this technology.

But mRNA vaccine research also has strong roots in the cancer field.

Dr. Kesari explained where he sees the potential for mRNA vaccines in cancer. “The great thing about mRNA [vaccines] are the manufacturing, scalability, and cost,” he said.

He used COVID-19 as an example. Scientists from China published the molecular code for the SARS-CoV-2 virus in January 2020. This allowed scientists and pharmaceutical companies with mRNA vaccine development expertise to initiate work on creating novel mRNA vaccines specifically designed to match the virus.

“It’s really built upon decades of research and informatics because understanding what’s a good vaccine [and] what’s not a good vaccine at the protein level, and then translating to the mRNA level has been built over many decades,” Dr. Kesari explained.

He drew a parallel between COVID-19 and the challenges he faces when treating patients with brain cancer.

Dr. Kesari sees great potential in mRNA vaccines as part of a wider arsenal to treat his patients. The speed and ease of manufacturing make this particular vaccine platform an attractive candidate for novel treatments.

Source: Medical News Today