Back to Top Skip to main content Skip to sub-navigation

DOD experts explain: The science behind the COVID-19 vaccines

Medical personnel in PPE, conducting lab tests Letzibeth Mendez-Rivera, a lab manager with The Emerging Infectious Disease Branch at the Walter Reed Army Institute of Research in Silver Spring, Maryland, studies coronavirus protein samples this summer. (Photo by Mike Walters, Walter Reed Army Institute of Research.)

Recommended Content:

MHS Toolkits and Branding Guidance | Coronavirus | COVID-19 Vaccine Efforts

Almost six weeks after the Food and Drug Administration issued emergency use authorization for the first two COVID-19 vaccines, many questions have arisen concerning their efficacy in attacking the SARS-CoV-2 virus and deadly COVID-19 disease.

To better understand how COVID-19 vaccines work, MHS Communications spoke to two medical experts who have been intimately involved in the Department of Defense’s effort to develop and roll out vaccines for Americans: Dr. Margaret Ryan, medical director of the Defense Health Agency’s Immunization Healthcare Division at the Pacific Region Vaccine Safety Hub in San Diego, California; and Air Force Col. (Dr.) Jessica Cowden, chief medical officer of the Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense and the Infectious Disease Programs at the Defense Institute for Medical Operations at Lackland Air Force Base in San Antonio, Texas.

The virus and the disease

SARS-CoV-2 virus, like other viruses, is an infectious agent that consists of genetic coding material called RNA [usually a single-stranded ribose sugar phosphate] or DNA [usually a double-stranded deoxyribose sugar phosphate] that is contained in a protein coat, Ryan stated. Viruses cannot reproduce themselves until they infect a living cell, she explained, so viral RNA or DNA cause an infected cell to make copies of the virus, thus infecting other living cells and potentially making people very sick in the process.

“In the case of SARS-CoV-2, the virus tends to infect cells in the human respiratory tract,” said Ryan. “The body responds to infection with inflammation, and people may experience fever, cough, and trouble breathing. The SARS-CoV-2 virus can also use its surface ‘spike protein’ to infect other cells in the body.”

The spectrum of illnesses the SARS-CoV-2 causes is called COVID-19 — or coronavirus disease from a pathogen first identified in 2019, she said. “People with COVID-19 can spread virus to nearby people from respiratory secretions after coughing, sneezing, or even talking.” 

However, asymptomatic people infected with COVID-19 may still spread virus, she explained. And “respiratory secretions on surfaces may also be picked up by people who handle these surfaces, although this may be a less common way that COVID-19 is spread,” she said. That’s why it is so important for all people to heed medical guidance and wear facemasks, wash hands frequently, and practice physical distancing.

As we have learned, some people react differently to the virus than others: Some get sick with COVID-19 while others remain asymptomatic. This is because the COVID-19 virus, as many others, can infect some people who never develop any symptoms, she said.

Three vials of COVID-19 vaccine on a table
The Puerto Rico National Guard began to vaccinate residents and personnel of the island's aegis against COVID-19 on January 27. The PRNG expects to complete the first and second doses by the middle of March. (Photo by Army National Guard Staff Sgt. Alexis Velez.)

“These asymptomatic people may mount an immune response to infection before experiencing symptoms, or they may tolerate infection without symptoms,” explained Ryan. “While it is not entirely clear why some people do not develop symptoms and some people develop only mild symptoms, we know some factors that increase risk of serious infection.”

For example, she said older age is an important risk factor for serious COVID-19 infection. “There is no absolute age when risk increases, but 80% of COVID-19 deaths have occurred in people older than age 65.”

Many underlying medical conditions can increase the risk of serious COVID-19, including but not limited to chronic lung, heart, and kidney disease; diabetes; cancer; and immune-compromising conditions, such as obesity and pregnancy. Smoking can also increase the risk for illness, she said.

New strains

Over the last weeks of 2020 and first weeks of 2021, new variants of SARS-CoV-2 have been identified across the globe, alarming the public and raising concerns about the efficacy of the vaccines.

“Coronaviruses are part of a large family of viruses that are capable of genetically evolving or changing over time,” explained Ryan. “In fact, SARS-CoV-2 likely arose from a major genetic change in a coronavirus that was first identified in 2019.”

According to Cowden, “genetic substitutions in the virus genome will lead to the emergence of new strains as SARS-CoV-2 continues to circulate in the human population throughout the world.” Some of these new strains, or mutations, may lead to increased or decreased “fitness” of the virus, that is, “the changes in how easily it transmits or in virulence — how sick it makes people. 

However, although some of these variants appear to be easily transmitted, they cause the same spectrum of symptoms, Ryan explained. “Spike-protein-based immune responses seem to be similar in new variants, which means current vaccines should be effective against these variants.”

Nonetheless, she said, scientists are examining the evolution of virus variants very carefully. Recent news reports from the United Kingdom say the new variant they identified among their population may not only be more contagious but could be more deadly as well.

How vaccines work

Pharmaceutical companies, universities, and government organizations around the world have been working against and around the clock since the beginning of the COVID-19 pandemic to develop a safe and effective vaccine to counter the rates of contagion. Pfizer-BioNTech and Moderna received the FDA’s emergency use authorization in the United States in mid-December 2020 for people ages 16 and older and 18 and older, respectively, but other promising candidates are in development by additional professional teams, including Janssen, AstraZeneca, and Novavax.

“The different vaccine candidates are all targeting the SARS-CoV-2 spike protein,” said Cowden. They work by presenting an antigen — a substance that the body does not recognize — to the body, she said.

The experts explained that antigens are introduced as a small piece of coding material, called messenger RNA (mRNA), into a few immune cells. It is encased in a lipid coat that allows it to enter only the outer part of the cells. It does not integrate into the person’s DNA or replicate, and it breaks down quickly, so it’s only present in the cell briefly.

“That mRNA then tells the cells to express ‘spike protein,’ resulting in the immune system making antibodies to destroy the spike protein,” said Ryan, adding that mRNA vaccines must be handled very carefully and often maintained at very cold temperatures to work properly.

Vaccines use different platforms to introduce the spike protein to the body to elicit the immune system’s response of blocking or killing the virus if a person becomes infected after vaccination, added Cowden. “Those antibodies then continue to be made by the body and can bind and/or neutralize the virus if an individual becomes infected after vaccination.”

Said Ryan: “The immune system also develops memory immune cells, so that any newly introduced spike protein would also be destroyed. Spike protein is similar to a protein on the coat of coronaviruses, so an immune response to spike protein can equate to immunity from coronavirus (SARS-CoV-2).”

Pfizer partnered with BioNTech to develop an mRNA vaccine that is administered in two injections given at least 21 days apart. Moderna developed a similar mRNA vaccine that also requires administration as two injections given at least 28 days apart. The mRNA technology in these does not include any virus.

Janssen, a subsidiary of Johnson & Johnson, developed a viral-vector vaccine to be administered in one injection. And AstraZeneca, in partnership with the University of Oxford, also developed a viral-vector vaccine that is to be administered in two injections at least 28 days apart. Both pharmaceuticals are likely to submit their products to FDA for emergency use authorization in the coming weeks.

“The Janssen and AstraZeneca/Oxford vaccines are both replication-deficient adenovirus-vectored vaccines,” said Cowden.

This means they use a different virus, such as measles or adenovirus, which is genetically engineered so that it can produce coronavirus proteins in the body and trigger the immune system to make antibodies against those proteins.

“After spike protein is expressed, the immune response is similar to that of mRNA vaccines: The immune system makes antibodies and memory immune cells that target spike protein. This response equates to immunity from SARS-CoV-2,” said Ryan.

The viruses used in viral-vector vaccines are weakened or inactivated, so they cannot cause disease or harm humans, said the experts. Viral-vector vaccines are also relatively fragile and must be maintained at temperatures that allow them to remain intact to work optimally.

Novavax developed an adjuvanted protein subunit vaccine to be administered in two injections at least 21 days apart. The experts explained this type of vaccine usually works by introducing a component of the virus — the antigen — into the body along with an adjuvant, a molecule composed of a cholesterol-like substance that stimulates the immune system, prompting the immune system to make antibodies against the protein antigen, resulting in immunity from the SARS-CoV-2 virus that causes COVID-19.

“Vaccines that use adjuvanted protein subunits introduce the spike protein directly,” said Ryan.

Unlike the others, this type of vaccine remains stable in refrigerated temperatures. When data from ongoing clinical trials is complete, Novavax will likely submit an application to FDA for emergency use authorization.

Why must some vaccines be kept in such cold temperatures?

Each vaccine is made differently. And each company is in different stages of testing the stability of its vaccine at different temperatures over time. However, the storage temperature requirements of each depend on the stability of the materials used to make the vaccine and conformation of the antigen, which in this case, is the spike protein, said Cowden.

She explained the SARS-CoV-2 virus requires a certain configuration of the spike protein so it can bind to ACE2 receptors, a type of enzyme, on human cells. “If the protein in the vaccine changes conformation so that that the [binding domain] RBD is not exposed, then the antibodies the body makes against the vaccine antigen won’t be targeted against it,” said Cowden. This may result in them not blocking the virus as well.

Person getting vaccinated
Navy Master Chief Petty Officer Joseph Martin, command master chief of Marine Forces, Special Operations Command, receives the COVID-19 vaccine at Naval Medical Center Camp Lejeune, North Carolina on Jan. 15. (Photo by Marine Corps Cpl. Jesula Jeanlouis.)

Why are we required to get two doses of some vaccines?

While single doses of vaccines prompt an immune response, Ryan explained that some vaccines must be taken in two doses to ensure a stronger and more long-lasting response in more people. In other words, while a primary shot will provide immunity, the second shot will boost it and build on the immunity from the first dose to generate a more durable response.

“When scientists begin to develop a vaccine, they look for immune responses in laboratory studies and initial small studies in humans,” said Ryan. “The scientists then select vaccine doses and timing that are most promising, and these vaccine schedules are used in large clinical trials.” 

In the case of COVID-19 vaccines, she said there is only strong information available on the doses and timing used in the large trials, for which most products required two-dose schedules.

How do we know vaccines are safe? 

According to Ryan, new medications and vaccines undergo rigorous safety reviews before they are approved for use in the United States. In fact, she said, initial studies must demonstrate safety before they demonstrate effectiveness.

“Safety continues to be evaluated closely in all phases of study and even after a new vaccine is approved for general use,” she said. “The manufacturers and federal authorities, including the Centers for the Disease Control and Prevention, FDA, and DOD, are evaluating the experiences of vaccine recipients very closely.”

Another factor to consider is the commitment from regulatory groups like FDA, said Cowden. “They have strict standards and regulations that must be followed to approve a vaccine or an antibody.”

In fact, she added, the FDA made its standards tougher for COVID vaccines by setting minimum requirements for the effectiveness of products submitted for approval. “By doing this, the FDA has confirmed their strong commitment to only approving a vaccine that could offer immunity to the majority of the population.”

In the case of COVID-19 vaccines that were recently authorized for use, more than 10,000 people received these products in studies, and more than 22 million doses had been administered in the United States under emergency use authorization as of Jan. 24, said Ryan. And although they are known to be reactogenic, or capable of causing a reaction, the side effects they cause — sore arms, headaches, fever — generally last no more than 1-3 days and can be treated with over-the-counter medicines, like ibuprofen or acetaminophen.

“All immediate allergic reactions have been successfully treated at the vaccination clinic sites,” she added. “No safety concerns have substantially changed the recommendation for the general public to receive these vaccines.”

Serious adverse reactions are much rarer but tend to get much more media coverage, said Ryan. “Serious allergic reactions have occurred in about 1 in 100,000 people immediately after vaccine administration.”

Still, “COVID-19 vaccines are among the most effective vaccines ever produced,” assured Ryan. “The safety of these vaccines will continue to be followed very closely, but people should feel confident in receiving these products.”

You also may be interested in...

Air Force takes steps to assure ‘unblinking’ operations, readiness and capabilities amid pandemic

Article
3/23/2020
Air Force medics and health personnel around the globe are resolutely following and ensuring compliance with guidelines issued by the Department of Defense and Centers for Disease Control and Prevention according to Air Force Lt. Gen. Dorothy Hogg.

Within the Air Force, our medics are executing all available measures to mitigate the spread of COVID-19

Recommended Content:

Combat Support | Public Health | Coronavirus | Coronavirus

A full night’s sleep could be the best defense against COVID-19

Article
3/23/2020
Sleep is critical for maintaining physical, cognitive and immunological dominance on and off the battlefield. Leaders must prioritize sleep as a valuable asset in maintaining readiness and resilience, especially in the context of multi-domain operations and increased health risks worldwide – including those risks associated with exposure to infectious diseases (U.S. Army photo by Robert Timmons)

Getting more sleep could dramatically improve your odds of avoiding infection

Recommended Content:

Combat Support | Public Health | Coronavirus | Coronavirus | Total Force Fitness

Addressing emotional responses to threat of Coronavirus

Article
3/20/2020
U.S. Air Force Master Sgt. Kathleen A. Myhre, 446th Airman and Family Readiness Center noncommissioned officer in charge, meditates outside the 446th Airlift Wing Headquarters building on Joint Base Lewis-McChord, Washington, Feb. 12, 2020. Myhre traveled to India in 2016 to study to become an internationally-certified yoga instructor. She now shares her holistic training with Reserve Citizen Airmen of the 446th AW. (U.S. Air Force photo by Staff Sgt. Mary A. Andom)

Even if you’re feeling healthy, medical professionals recommend staying home and limiting social contact as much as possible

Recommended Content:

Medical and Dental Preventive Care Fitness | Psychological Fitness | Physical Fitness | Combat Support | Public Health | Coronavirus | Coronavirus

COVID-19 Life Support Training Extension

Publication
3/19/2020

The purpose of this memorandum is to set policy guidance within the Military Health System for American Red Cross life support training (First Aid/cardiopulmonary resuscitation (CPR)/automated external defibrillator (AED), Basic Life Support (BLS), Advanced Life Support (ALS), and Pediatric Advanced Life Support (PALS)).

Recommended Content:

Coronavirus

Place addresses DHA COVID-19 response

Article
3/19/2020
Lt. Gen. Ronald Place, director of the Defense Health Agency, and Rear Adm. Bruce Gillingham, surgeon general of the Navy, discuss plans for additional COVID-19 response efforts with the Pentagon Press Corps.

Crisis Action Team part of broad-based effort

Recommended Content:

Combat Support | Public Health | Coronavirus | Coronavirus

DoD ready to help with Coronavirus, but capability limited

Article
3/17/2020
Misook Choe, a laboratory manager with the Emerging Infectious Disease branch at the Walter Reed Army Institute of Research in Silver Spring, Md., runs a test during research into a solution for the new coronavirus, COVID-19, March 3, 2020. The Emerging Infectious Diseases branch, established in 2018, has the explicit mission to survey, anticipate and counter the mounting threat of emerging infectious diseases of key importance to U.S. forces in the homeland and abroad. (U.S. Army Sgt. Michael Walters)

The DoD has only about 2% to 3% of the number of hospital beds that the private sector has

Recommended Content:

Combat Support | Public Health | Coronavirus | Coronavirus

How DHA monitors the spread of health outbreaks

Article
3/13/2020
The Armed Forces Health Surveillance Branch (AFHSB) is the central epidemiologic resource for the U.S. Armed Forces, conducting medical surveillance to protect those who serve our nation in uniform and allies who are critical to our national security interests. AFHSB provides timely, relevant, actionable and comprehensive health surveillance information to promote, maintain, and enhance the health of military and military-associated populations. (U.S. Air Force photo by Tech. Sgt. Nathan Lipscomb)

The Defense Health Agency works as a combat support agency to the military services and Military Health System

Recommended Content:

Combat Support | Public Health | Coronavirus | Coronavirus

DoD issues flexible instructions on response to Coronavirus

Article
3/13/2020
This illustration, created at the Centers for Disease Control and Prevention (CDC), reveals ultrastructural morphology exhibited by coronaviruses. The illness caused by this virus has been named coronavirus disease 2019 (COVID-19). (CDC Illustration)

The memo covers aspects from before the outbreak through all levels of infection

Recommended Content:

Combat Support | Public Health | Coronavirus | Coronavirus

Terry M. Rauch, Ph.D., M.P.H., M.B.A. Acting Deputy Assistant Secretary of Defense Force Health Protection and Readiness Regarding U.S. Biodefense and Response to the Novel Coronavirus Outbreak [Testified] Before the House Committee on Oversight and Reform

Congressional Testimony
3/11/2020

Recommended Content:

COVID-19 Vaccine Toolkit | COVID-19 Vaccine Toolkit | Coronavirus

COVID-19: Know what the terms mean

Article
3/10/2020
Soldiers stationed on U.S. Army Garrison Casey conduct pre-screening processes on individuals awaiting entry to the base, USAG-Casey, Dongducheon, Republic of Korea, Feb. 26, 2020. Additional screening measures of a verbal questionnaire and temperature check are in response to the heighted awareness of Coronavirus (COVID-19) following a surge in cases throughout the Republic of Korea and are meant to help control the spread of COVID-19 and to protect the force. (U.S. Army photo by Sgt. Amber I. Smith)

Learning the language can help you stay safe

Recommended Content:

Coronavirus | Public Health | Combat Support | Coronavirus

Coronavirus: What you need to know

Article
3/6/2020
A Guardsmen with the 341st Military Intelligence Battalion conducts translation work on a safety message regarding the best practices for avoiding the novel coronavirus for the Washington Department of Health on Feb. 9, 2020 at the Information Operations Readiness Center, Joint Base Lewis-McChord, Wash. (Courtesy Photo)

Although news stories and images contain many reports of people wearing surgical masks to ward off the virus, that's not recommended

Recommended Content:

Global Health Engagement | Public Health | Coronavirus | Coronavirus

DoD makes plans to combat Coronavirus

Article
3/4/2020
Defense Secretary Dr. Mark T. Esper and Army Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff, speak to reporters at the Pentagon, March 2, 2020. (DoD photo Lisa Ferdinando)

The number one priority remains to protect our forces and their families

Recommended Content:

Coronavirus | Public Health | Combat Support | Coronavirus

MHS prepared to support interagency coronavirus response

Article
2/6/2020
Airmen assist one another in donning their personal protective equipment, while on-board an Air Force C-17 Globemaster III during transportation isolation system training at Joint Base Charleston, South Carolina. Engineered and implemented after the Ebola virus outbreak in 2014, the TIS is an enclosure the Department of Defense can use to safely transport patients with diseases like novel coronavirus. (U.S. Air Force photo by Senior Airman Cody R. Miller)

From R&D to force health protection, MHS protects DoD personnel and families

Recommended Content:

Global Health Engagement | Public Health | Coronavirus | Coronavirus

DoD releases guidance to protect forces from novel coronavirus

Article
1/31/2020
The novel coronavirus is a variant of other coronaviruses, such as this colorized transmission electron micrograph of Middle East respiratory syndrome (MERS) virus particles (blue) found near the periphery of an infected VERO E6 cell (yellow). Image captured and color-enhanced at the NIAID Integrated Research Facility in Fort Detrick, Maryland. (Photo by NIAID)

Basic infection controls offer best defense against illness

Recommended Content:

Global Health Engagement | Public Health | Coronavirus | Coronavirus

Coronavirus: What providers, patients should know

Article
1/24/2020
Many forms of coronavirus exist among both humans and animals, but this new strain’s has caused alarm. (CDC graphic)

What to do now that virus has appeared in U.S.

Recommended Content:

Global Health Engagement | Public Health | Coronavirus | Coronavirus
<< < ... 36 37 38 39 40  ... > >> 
Showing results 586 - 600 Page 40 of 41

DHA Address: 7700 Arlington Boulevard | Suite 5101 | Falls Church, VA | 22042-5101

Some documents are presented in Portable Document Format (PDF). A PDF reader is required for viewing. Download a PDF Reader or learn more about PDFs.