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August 2021

The arrival of COVID-19 vaccines brought hope that 2021 could mark the beginning of the end of this devastating pandemic. While the rapid development of these vaccines is an extraordinary scientific achievement, much work remains to ensure that people across the United States and world can access a vaccine—and achieving that will require continued investment in research and development (R&D) of COVID-19 vaccines.

To help you sort through the barrage of information and news on COVID-19 vaccines, GHTC answers frequently asked questions about COVID-19 vaccine R&D.

Last updated: August 27, 2021

The following vaccines have been approved for emergency use authorization (EUA) or full market authorization in the United States by the US Food and Drug Administration:

  • Pfizer/BioNTech vaccine, approved for EUA December 11, 2020, for individuals ages 16 and up; approved for EUA May 10, 2021 for 12- to 15-year olds; full authorization August 27, 2021 for 16 and up
    • US government supported development through purchase commitment via funds from the Biomedical Advanced Research and Development Authority (BARDA) and the Department of Defense (DoD) as part of Operation Warp Speed (OWS).
  • Moderna vaccine, approved for EUA December 18, 2020, for individuals ages 18 and up
    • Was codeveloped by scientists at the US National Institute of Allergy and Infectious Diseases (NIAID) with additional financial support from BARDA as part of OWS.
  • Johnson & Johnson vaccine, approved for EUA February 27, 2021, for individuals ages 18 and up
    • NIAID and BARDA supported development as part of OWS.


Additionally, the following vaccines have been approved for emergency use by stringent regulatory authorities of other nations or the World Health Organization:


The following vaccines have either received full approval or emergency use approval from non-stringent regulatory authorities. Note: There is less public, verifiable data on these vaccines:


Additionally, there are more than 90 vaccine candidates now in clinical trials in humans. Among those, the most advanced in phase 3 trials include: 

Among those vaccines approved by stringent regulatory authorities, all have proved highly effective in preventing illness, particularly severe illness, in clinical trials:

  • The Pfizer/BioNTech vaccine was shown to be 95 percent effective in preventing COVID-19 illness in clinical trials.
  • The Moderna vaccine was shown to be 94 percent effective in preventing COVID-19 illness in clinical trials.
  • Russia's Sputnik V vaccine was shown to be 91.6 percent effective in preventing illness in clinical trials.
  • The AstraZeneca/University of Oxford vaccine was shown to be 76 percent effective in preventing illness and 100 percent effective in preventing severe disease in a recent US-based clinical trial, while pooled results from trials in the United Kingdom, South Africa, and Brazil showed it at roughly 62 percent efficacy in preventing illness.
  •  Johnson & Johnson’s vaccine was found to be 66 percent effective overall in preventing moderate to severe illness, with an efficacy at 72 percent among participants in the United States. Overall, the vaccine was 85 percent effective in preventing severe illness.
  • The Sinopharm/Beijing Institute vaccine has reported efficacy rates in preventing illness of 79 percent and 86 percent from different clinical trials.
  • CanSino’s Convidecia vaccine was shown to be 65 percent effective in preventing illness in clinical trials.
  • Sinovac’s CoronaVac vaccine was 51 percent effective in preventing symptomatic disease and 100 percent effective in preventing severe COVID-19 and hospitalization

It can be misleading to compare vaccine efficacy results exactly head-to-head because of the differences in what each trial was measuring for, when and where the trials took place, and how widespread different variants were at that time and in that geography. The important takeaway is that all approved vaccines have been shown to be highly effective, particularly in preventing severe forms of illness and death. For a more detailed look at the impact of virus variants on vaccine efficacy, click here.

Evidence shows that COVID-19 vaccines do reduce the likelihood of a person spreading the virus, though scientists are still studying the issue to understand to what degree and what impact variants are having. Efficacy results from the original clinical trials only measured how much a vaccine reduced the risk of an individual becoming symptomatic with COVID-19 illness. The trials were not able to measure whether the vaccines also prevent vaccinated individuals from transmitting the virus to others as asymptomatic spreaders.

In spring 2020, several real-world studies came out that offered an optimistic picture. For example, a study by the Centers for Disease Control and Prevention found the Pfizer/BioNTech and Moderna vaccines reduced a person’s risk of infection by 90 percent. (Without infection, one can't spread the virus). While an English study conducted among households with a mix of vaccinated and unvaccinated individuals, found that those individuals who did become infected after being vaccinated (known as breakthrough infections) were half as likely to pass on the infection to others compared to unvaccinated individuals who were infected. Thus, at the time experts believed there was little risk of spread by vaccinated individuals.

Yet as the Delta variant has become more widespread, the picture has become hazier. A study in July of an outbreak in Provincetown, Massachusetts found that three-quarters of those infected were fully vaccinated. That high share of infections among the vaccinated suggests there was at least some onward transmission by the vaccinated fueling the spread. In addition, the study found that some unvaccinated people had similar levels of virus in their nose as the infected, unvaccinated. This viral load data is not proof that those with breakthrough infections are just as infectious as the infected, unvaccinated, as some outlets erroneously reported, as other factors still impact likelihood of onward transmission.

While research remains ongoing, we know now is that overall, vaccinated people are far less likely to transmit the virus, because they are far less likely to become infected from the start, but if they do become infected, it’s possible for them to spread the virus, yet likely not to the extent the unvaccinated do.

Yes, risks of side effects are very low. While COVID-19 vaccines were developed and approved more quickly than has historically been the case for other vaccines, all vaccines approved by the US Food and Drug Administration and other stringent regulatory authorities have gone through a rigorous process of being tested via clinical trials in tens of thousands of volunteers to ensure they are safe and effective. These trial results were then reviewed and verified by independent scientists, who informed the approval decisions by these regulatory authorities.

Since initial emergency use authorization, there have been some serious side effects reported, but in each case, they are extremely rare. Earlier this year, a causal link was established between the AstraZeneca vaccine and rare cases of blood clotting disorders. A few cases of clotting disorders have also been reported among those who received the Johnson & Johnson (J&J) vaccine. But in both cases, the risk level is very low. For context, 4 out of 10,000 women experience a blood clot from taking oral contraception, while there were just 1.9 cases of blood clots per 1 million J&J doses administered. Regulatory authorities have emphasized that that the benefits of these vaccines outweigh the risk. In the case of the AstraZeneca vaccine, some regulatory authorities are recommending that individuals under 40 receive an alternative vaccine, if available, out of an abundance of caution.

There have also been some reported cases of heart inflammation, mostly among young men and adolescents, following vaccination with the Pfizer/BioNTech and Moderna mRNA vaccines, as well as allergic reactions among those with a history of allergic reaction. But both are extremely rare. In the case of heart inflammation, confirmed cases by the Centers for Disease Control and Prevention (CDC) are around 1 for every 1 million doses administered, and almost all the cases were resolved with little treatment. Health officials have continued to stress that the risk of illness or death from COVID-19 significantly outweighs the risk of serious side effects from vaccines.

It is too early to know for certain, and the answer depends on a number factors including a person’s age and immune system state, and whether one is referring to protection from infection or protection from serious illness.

This summer, some countries including the United States, began offering a third booster shot of the Pfizer/BioNTech and Moderna vaccines to individuals who were immunocompromised, after data demonstrated these individuals had a weaker immune response and were more likely to experience breakthrough infections. The United States, as well as some other countries, also announced plans to begin rolling out booster shots to their broader population, in cascading priority starting with those at highest risk of illness. In the United States, the shots are recommended to occur eight months after people received their second shot.

In making their decision, US officials have noted recent data showing a rise in breakthrough infections among the vaccinated as the Delta variant has become widespread. However, the same studies show that despite a rise in infections, the vaccines remain highly effective in preventing severe illness, hospitalization, and death. It remains challenging to disaggregate what is driving the declines in vaccine efficacy against infection. It could be waning immune response over time, the ability of the Delta variant to more readily evade vaccines, easing of other mitigation efforts like mask wearing and social distancing which is leading to increased virus exposure, or some combination of all three. Scientists are continuing to study the issue to inform planning around booster shots.

The answer is yes, but effectiveness against infection is falling. The positive news is that studies continue to show that the vaccines are highly effective in preventing severe illness, hospitalization, and death, despite the emergence of variants of concern. However, the same research also suggests protection against infection has weakened over recent months. Taken together, three recent studies in the United States indicate overall that vaccines in use in the country have an effectiveness of roughly 55 percent against all infections, 80 percent against symptomatic infection, and 90 percent or higher against hospitalization. It is important to note that while this reduction in efficacy against infection is in part being driven by variants, including the widespread Delta variant which is causing more breakthrough infections than other forms of the virus, there are additional factors that could be influencing this decline including waning immune response over time and reduction in other mitigation efforts which could be exposing more people to the virus than in the early days of the vaccine roll out.

For vaccines used more heavily outside the United States, evidence suggests a similar pattern of reduced efficacy caused in part by certain variants. For example, a UK study from July found the AstraZeneca/University of Oxford vaccine was 67 percent effective at preventing symptomatic illness from the Delta variant, compared to 74.5 percent against the Alpha variant. Meanwhile, a small trial in South Africa found that the AstraZeneca/University of Oxford vaccine was not effective in protecting trial participants from mild to moderate illness caused by the Beta variant prevalent in South Africa, leading the country to halt use of that vaccine, though research continues as to its efficacy in preventing severe illness, hospitalizations, and death. In clinical trial results from earlier in the year, Johnson & Johnson also reported that while its vaccine was 74 percent effective in preventing moderate to severe illness in the United States, where the original virus was prevalent at the time, it was only 52 percent effective in South Africa, where the Beta variant was dominate.

Research into the impact of variants on vaccine efficacy is actively ongoing. Several vaccine makers including Pfizer/BioNTech, Moderna, and AstraZeneca/University of Oxford have already begun testing booster shots or adapted versions of their vaccine designed to address variants. However, the emergence of variants has changed the game and will certainly add complications and time to efforts to bring the pandemic under control.

The first-to-market COVID-19 vaccines were approved for emergency use just 11 months after scientists first got their hands on the genetic sequence of the virus, an extraordinary achievement, especially given vaccine development has typically taken a decade or more.

A number of factors contributed to this success. First, while SARS-CoV-2 was a brand-new virus, scientists weren’t starting fully from scratch on vaccine development, since science builds on science. Previous vaccine research on similar viruses like Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS), as well as other infectious diseases like HIV, malaria, Ebola, and influenza, helped researchers know where to begin and also advanced development of different types of vaccine approaches or platforms—which serve as a type of “template” for scientists to use in creating new vaccines. Two of the first approved vaccines, the Pfizer/BioNTech and Moderna vaccines, make use of a new platform approach called mRNA. (mRNA vaccines have been studied for decades, but this marks the first time vaccines using the approach have come to market.) Instead of using a weakened or inactivated form of a virus to trigger an immune response, mRNA vaccines give “instructions” to our cells to create a piece of the virus’s protein to elicit an immune response, and key here, because in this approach one can in essence “plug in” a new viral genetic sequence to create a new vaccine, mRNA vaccines are faster to design from the get-go to begin testing, which sped up the process to some degree.

Second, and most significant, developers were able to shorten and stack several stages of the product development process to run in parallel, including clinical trials, which typically take five to ten years, and commercial manufacturing, which often takes another two to five years. Vaccines normally go through three phases of clinical trials to test for safety, immune response, and efficacy in subsequently larger populations at each stage. In the case of COVID-19 vaccines, trials for safety and immune response (phases 1 and 2a) were often combined, as were trials for efficacy (phases 2b and 3), thus shaving off months between each trial phase, as you consider the time required for protocols to be prepared, approved, and for patients to be recruited. Additionally, product developers began manufacturing stock of their vaccines as soon as the vaccines were first developed, rather than waiting for this to begin after vaccines were shown to be effective and approved by regulators, as is normally the case. This was a huge financial risk (that governments and philanthropists financially backed, making it possible) that could have and still could result in unusable, ineffective vaccines, but it was key to significantly accelerating the speed at which vaccines reached patients. For example, this is why the first doses of the Pfizer/BioNTech and Moderna vaccines were able to hit the market within days of each being approved.

Third, regulatory agencies, like the US Food and Drug Administration (FDA), worked quickly to communicate with product developers about thresholds for approval and to review and approve trial protocols, applying lessons learned from vaccine trials during the West African Ebola crisis. The FDA and other regulators also used an expedited approval process designed for global health emergencies to approve vaccines for emergency use. 

Finally, vaccine development efforts were facilitated by an unprecedented level of public-private sector collaboration and government funding. Normally, companies and their funders want to wait to see candidates successfully proceed through each subsequent stage of the product development process before putting in additional funding for the next stage, which can slow the process, but in this case significant up-front funding commitments for R&D and procurement allowed developers to plan for the end-to-end process from the start, thereby expediting the development process.

One of the first significant challenges is manufacturing—producing enough vaccines to meet global need. Vaccine manufacturing is inherently a complex process. It involves creating biological products that must be produced with great consistency and protected from the introduction of outside contaminants to ensure product safety. That means manufacturers must routinely test batches and maintain careful safety protocols, with their facilities and processes reviewed and approved by regulators. Because of the complexity of vaccine manufacturing, most production facilities are purpose-built for specific vaccines, and there are startup costs and time involved in building facilities or retrofitting them for new vaccines. Additionally, every element of the final packaged vaccine, from the raw materials used in it, to the glass vials it’s stored in, to the dry ice it’s packaged in, presents opportunities for individual supply chain breakdowns and delays that ultimately can delay overall production timelines. While vaccine developers are working to increase manufacturing capacity, both by expanding and building their own facilities and partnering with generic or contract vaccine manufacturers to multiply production volume, producing enough vaccines to vaccinate the entire world will still take some time. Assuming two-dose vaccines, it will take the production of 12 to 15 billion vaccine doses to get about 80 percent of the global population immunized. With several high-income countries already announcing plans to provide booster shots to their citizens, this challenge of manufacturing enough vaccine doses becomes even more pronounced.

The second set of challenges is around distribution and logistics. Simply put, it is hard to successfully get billions of doses to billions of people worldwide. Global and national guidelines must be translated to state and local action by a number of coordinated players, including government entities and private-sector health providers. As vaccines are shipped and stored for administration, they must be constantly kept at the right temperature to ensure they remain effective, which is commonly referred to as maintaining the cold chain. Among the first-to-market vaccines, the Moderna and Pfizer/BioNTech vaccines must be stored in pharmaceutical freezers that many facilities don’t have or can’t get or afford. This makes these vaccines logistically more difficult to distribute in smaller, rural health facilities that lack required infrastructure, whether that’s in a town in Iowa or a village in Sierra Leone. While the AstraZeneca/University of Oxford, Sputnik V, CanSino, Sinopharm/Beijing Institute, and Johnson & Johnson vaccines requires standard refrigeration that is much easier to maintain, even that can still pose a challenge for administration in some low-resource settings worldwide that lack reliable access to electricity. Another logistical challenge is ensuring patients receive the second dose of various two-dose vaccines at the right time to experience full protection, which will require significant follow-up on the part of health providers. It also requires double the syringes, storage capacity, and staff time. It’s not just the supply chain of actual vaccine doses that can create delays, but also supplies of syringes, personal protective equipment, and other tools health workers need for vaccine administration.

The third set of challenges is related to persuading the public to take a vaccine. In the United States, for example, around two in ten Americans still report they do not plan to get a COVID-19 vaccine and just under 60 percent of eligible individuals are fully vaccinated. Distrust is even greater among historically disadvantaged populations, including people of color. Vaccine hesitancy is not unique to the United States and will present an ongoing challenge in reaching high levels of vaccine coverage worldwide.

Finally, money is a challenge. This all carries costs. Within the United States, state and local health departments are struggling to shoulder these new costs. At the global level, many low- and middle-income countries can’t afford to obtain and distribute vaccines to their populations, creating a need for additional support from donor countries.

Given the challenges above, many experts believe that while significant portions of the population in the United States and high-income countries may have access to a vaccine by the end of 2021, billions of people worldwide may not receive access until 2022 or as late as 2024. There is also significant likelihood that COVID-19 will become another endemic disease, meaning that though cases will decline significantly in communities with high vaccination coverage, the disease will still continue to circulate to some degree and cause sporadic outbreaks among those unvaccinated. 

Simply stated: 1) where a person lives should not determine whether they live or die; 2) no one is truly safe until everyone is safe; 3) COVID-19 could undo decades of progress in other health and development investments; and 4) it is a smart economic decision.

The circumstances of a person’s birth and where they live should not determine their right to health. It is the morally right thing to do to ensure everyone in the world can access a vaccine, whether they live in a small town in Nevada or a remote community in Nigeria.

It is also the smart thing to do. Even if high-income countries (HICs) achieve relatively high immunization coverage within their own borders, if the virus continues to significantly spread among unvaccinated populations worldwide, HICs will continue to see some level of reintroduction of the virus and small outbreaks among their own unvaccinated population. And given remaining uncertainty about how long vaccine protection lasts, reintroductions over the coming years could further complicate efforts to keep the virus in check domestically. Similarly, the slower the global scale-up of the vaccine is, the more likely we are to see the emergence of additional new variants of the virus. As discussed, these variants are already complicating vaccination efforts, thus rendering already vaccinated domestic populations at higher risk from COVID-19. No one is safe until everyone is safe.

If we do not support an adequate global response to COVID-19, we also risk undermining decades of investments in health and development programs. Already, the pandemic has set back global health progress by about 25 years. Routine immunization programs have dropped to levels last seen in the 1990s, and as many as 115 million people could be pushed into extreme poverty. UNICEF estimates an addition 6,000 children will die of preventable causes each day due to pandemic-related disruptions to health care, and The Global Fund to Fight AIDS, Tuberculosis and Malaria estimates an additional 1 million people could die of AIDS and tuberculosis in 2021. Through strong funding and decisive action to support vaccine scale-up worldwide, these trends can be reversed.

Supporting COVID-19 vaccination worldwide is also a sound economic decision. A recent analysis suggests that leaving low- and lower-middle-income countries (LLMICs) to fend for themselves in responding to COVID-19 will put decades of economic progress at risk for both LLMICs and advanced economies alike. According to the analysis, the cumulative economic benefit of an equitable vaccine solution accrued to ten top donor countries alone would be US$13 billion in 2020-2021 and $466 billion over the next five years, more than 12 times the estimated cost to do so. The United States has the most to gain economically for this effort, with $78.8 billion in potential benefits for 2021-2021 and $207.1 billion over the next five years.

The global mechanism that has been stood up to facilitate global vaccine research and access, which is modeled in the above economic analysis, is the Access to COVID-19 Tools Accelerator (ACT-A)’s COVAX Facility. COVAX was created to maximize the world’s chances of successfully developing COVID-19 vaccines and manufacturing and distributing them in the quantities needed to end this crisis. Through an advance market commitment and partnership involving more than 180 countries, COVAX is working to advance R&D and procure vaccines doses for participating countries, including doses for its 92 poorest countries, many of which have not been able to secure bilateral deals independently and are dependent on the facility for their population. COVAX is co-led by the World Health Organization; the Coalition for Epidemic Preparedness Innovations (CEPI), which leads the R&D side of its work; and Gavi, the Vaccine Alliance, which leads procurement and distribution efforts in partnership with UNICEF. The Biden-Harris administration announced in January 2021 that the United States was joining ACT-A and COVAX; and more recently the administration pledged to donate and purchase vaccines to support global efforts.

There are a number of reasons to continue investing in COVID-19 vaccine R&D. First, more successful vaccines mean more available doses and production capacity. Manufacturing of vaccine stock is already underway for many of the candidates in late-stage clinical development. Thus, it is important to continue to support those efforts to fruition, because if they prove effective, the moment these vaccines are approved, more doses become immediately available and the world’s overall manufacturing capacity for vaccines is increased.

Second, while global supply of vaccines remains limited, we must optimize what we have. Research examining the impact of mixing and matching different vaccine types or spreading out time between vaccine doses could help officials maximize public health impact while the world races to expand supply.

Third, we must ensure existing vaccines continue to remain effective. As discussed previously, there is still much known about how long vaccines will provide protection, their effectiveness against emerging variants and to what degree vaccines might need to be adapted against them, and more that requires continued study and investments in research.

Finally, to achieve aspirations to immunize the world, we will need second and third generation vaccines with characteristics that make them easier to deliver—like being single-dose and thermostable—as well as easier to manufacture in volume and more affordable. This will be especially important for reaching people in low-resource settings worldwide where barriers like lack of reliable cold chains and access to nearby health facilities can necessitate different types of tools. When vaccines are developed, the first ones to market are often less thermostable (meaning they must be kept at colder temperatures). That is the case with the Pfizer/BioNTech and Moderna vaccines, which must be kept at frozen temperatures for longer term storage. But over time, through continued research, developers often succeed in creating versions of a vaccine that can be stored at milder temperatures by adding new elements to the formulation. Further research can also lead to the creation of vaccines that are single-dose and thus easier and less costly to implement. Of the eight vaccines approved by stringent regulatory authorities and/or the World Health Organization, only two—Johnson & Johnson and CanSino—are single-dose. The other six—Pfizer/BioNTech, Moderna, AstraZeneca/University of Oxford, Sputnik V, Sinopharm/Beijing Institute. and Sinovac—all require two doses. Companies are also pursuing development of easier-to-administer formulations of COVID-19 vaccines, such as oral formulationsinhalable formulations, and versions administered by painless microneedle patches that stick on like a Band-Aid. Each of these innovations would make it easier to get vaccines to people in every corner of the globe. Researchers are also pursuing development of combination flu and coronavirus vaccines and universal coronavirus vaccines that could protect against multiple coronaviruses at the same time.

Yes. Based on current projections, it could take another two to four years to see significant portions of the global population vaccinated, and there is a high likelihood the virus will become endemic and continue to circulate at some level. There are also individuals, like certain immunocompromised people, that are unable to take vaccines. Thus, we will continue to need other solutions for COVID-19 including treatments, treatment as prevention approaches, and diagnostics, alongside continued use of public health practices like social distancing and masks.

While there are now a multitude of diagnostics on the market and many countries have made relative gains in increasing testing capacity, there is still a pressing need for more highly effective, low-cost, rapid point-of-care diagnostics that can be produced and deployed at mass scale. Similar to a home pregnancy tests, these types of tests provide a quick result, without a lab, and can be taken at home or at a health facility. While there are a few types of these tests now available, volume availability still remains low, and these antigen tests are often more likely to produce false negatives than traditional lab-based polymerase chain reaction tests, so further research to validate and improve these tools must continue. The emergence of new variants of COVID-19 is also complicating testing, as some existing tests are proving less effective in picking up these strains, underscoring the need for continued diagnostic research and validation.

In the therapeutic space, scientists have yet to discover a highly effective treatment option, underscoring the need for continued research. Only one treatment, remdesivir, has received full approval by the US Food and Drug Administration (FDA), but research suggests it may provide only a modest benefit to patients, and likewise evidence has been mixed for other antiviral treatments being studied. Research suggests repurposed steroids reduce deaths by about one-third among seriously ill patients by tamping down the immune system’s overreaction to the virus, but they are not recommended for individuals with mild disease. Combination monoclonal antibody therapies, which have been authorized by the FDA for emergency use, have shown promise in clinical trials in treating those in an early state of infection but have shown less promise in treating those with more severe illness. Monoclonal antibodies have also proven vulnerable to resistance from variants and are a challenging category of therapeutics to scale up worldwide, as current options are expensive to manufacture and most require intravenous infusion and a high volume of treatment.  But product developers are pursuing research to produce monoclonal antibody therapies that can be delivered via a shot, just under the skin or into the muscle, and can be produced more easily and affordably, in the hopes of making this option more accessible worldwide.

GHTC is encouraging US policymakers to continue to provide additional supplementary funding, as needed, for US agencies now engaged in COVID-19 vaccine R&D and rollout, including the National Institutes for Health, Biomedical Advanced Research and Development Authority, Centers for Disease Control and Prevention, and Department of Defense. To specifically support the international side of the COVID-19 research response in the near and long term, GHTC is recommending: