Efficacy Across Different Groups
A consistently high efficacy was observed in the clinical trials across age groups, sex, race, ethnicity and people with underlying medical conditions.
This means after getting two doses of the Pfizer vaccine, more than 9 out of 10 people are protected against COVID-19 regardless of their age, health status or ethnic group.
What Do We Know About A Single Dose Of Pfizer
Clinical trials of the Pfizer vaccine were designed to test the efficacy of the vaccine more than one week after the second dose. However, these trials also provided the first hints that a single dose could offer some protection as early as 12 days afterwards.
Real world data now supports these early observations a single dose is highly effective against hospitalisation four weeks after vaccination.
Preliminary data also suggest people who become infected with SARS-CoV-2 after one dose of the Pfizer vaccine are up to 50% less likely to transmit that infection to other members of their household.
Coronavirus Disease : Vaccines
There are several COVID-19 vaccines validated for use by WHO . The first mass vaccination programme started in early December 2020 and the number of vaccination doses administered is updated on a daily basis on the COVID-19 dashboard.
The WHO Emergency Use Listing process determines whether a product can be recommended for use based on all the available data on safety and efficacy and on its suitability in low- and middle-income countries. Vaccines are assessed to ensure they meet acceptable standards of quality, safety and efficacy using clinical trial data, manufacturing and quality control processes. The assessment weighs the threat posed by the emergency as well as the benefit that would accrue from the use of the product against any potential risks.
In line with their national regulations and legislation, countries have the autonomy to issue emergency use authorizations for any health product. Domestic emergency use authorizations are issued at the discretion of countries and not subject to WHO approval.
As of 26 November 2021, the following vaccines have obtained EUL:
If you live in a country where vaccines are available to more people beyond these priority groups, get vaccinated as soon as it is your turn.
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Ial Vaccination Can Be Risky
While a single dose of either vaccine provides some benefits, relying on partial vaccination for people who are vulnerable or working in high-risk roles is problematic. Its critical we fully vaccinate frontline health-care workers, quarantine workers and people who work and live in aged and disability care as soon as possible.
Another challenge is that all current COVID vaccines are based on the original virus strain but variants now make up the majority of infections in many countries. Some variants are targeted less effectively by vaccines, particularly after only one dose.
Preliminary data suggests that while two doses of the Pfizer vaccine are 88% protective against symptomatic infection with the B.1.617.2 variant, a single dose is only 33% effective.
A similar variant, called B.1.617.1, is behind the current outbreak in Victoria and may respond similarly. This makes it even more important to ensure frontline workers receive both vaccine doses as quickly as possible.
In a pooled analysis of Pfizer and AstraZeneca, older people had lower rates of protection than younger people after a single dose, although older people were protected just as well as younger people after two doses.
Effectiveness Of Mrna Bnt162b2 Covid
- Sara Y TartofCorrespondenceCorrespondence to: Dr Sara Y Tartof, Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA 91101, USAAffiliationsDepartment of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USADepartment of Health Systems Science, Kaiser Permanente Bernard J Tyson School of Medicine, Pasadena, CA, USA
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Covid Vaccine Immunity Is Waning How Much Does That Matter
For those vaccinated against COVID-19, antibody levels eventually wane, but this is not the whole story.Credit: Kateryna Kon/Science Photo Library
Six months ago, Miles Davenport and his colleagues made a bold prediction. On the basis of published results from vaccine trials and other data sources, they estimated that people immunized against COVID-19 would lose approximately half of their defensive antibodies every 108 days or so. As a result, vaccines that initially offered, say, 90% protection against mild cases of disease might only be 70% effective after 6 or 7 months.
It felt a little bit out on a limb at the time, says Davenport, a computational immunologist at the University of New South Wales in Sydney, Australia. But on the whole, his groups predictions have come true.
Immunological studies have documented a steady decline of antibody levels among vaccinated individuals. Long-term follow-up of vaccine trial participants has revealed a growing risk of breakthrough infection. And health-care records from countries such as Israel, the United Kingdom and elsewhere all show that COVID-19 vaccines are losing their strength, at least when it comes to keeping a lid on transmissible disease.
How Is Ecdc Supporting The Vaccination Rollout
The development of strategies and national plans for the deployment of COVID-19 vaccines is the responsibility of EU/EEA countries. This also includes the prioritisation carried out at national level on population groups for COVID-19 vaccination, and the vaccine rollout.
ECDC supports these efforts by working closely with EU/EEA countries and the European Commission to monitor the rollout of COVID-19 vaccines and develop scientific evidence and relevant technical guidance that can inform national priorities and decision-making.
ECDC also facilitates dialogue and exchanges between countries, supports preparedness activities, and provides regular overviews of vaccination deployment strategies and plans.
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Phase Two And Three Clinical Trials Vaccine And Placebo
The efficacy of the Pfizer vaccine was tested in about 44,000 participants aged 16 years and over where COVID-19 was already circulating in communities. About half of these participants were randomised to receive the vaccine and the other half received a saline placebo.
The trial looked at how many people got COVID-19 symptoms after they were vaccinated compared to how many got COVID-19 after getting the placebo.
Participants had two doses of the vaccine or placebo, getting their second dose within 19 to 42 days after their first dose. They were then closely monitored and evaluated for at least 2 months after their second dose.
Should That Immune Memory Give Durable Protection Against Severe Disease
For the most part, it should. But, says Theodora Hatziioannou, a virologist at the Rockefeller University in New York City, if protection from disease relies at any level on circulating neutralizing antibodies and those molecules are clearly on the decline then, yes, the longer out you are from natural infection or from vaccination the worse you will be.
Real-world data from diagnostic-testing records and hospital databases suggest that this might be the case. In Israel, for example, elderly people who got their shots at the beginning of the year seemed to have almost double the risk of severe illness during a July outbreak compared with similar individuals who were immunized more recently. As researchers reported this week, older individuals given a third dose of vaccine were less likely to become infected and much less likely to develop severe disease than those who had not received the boosters.
Third-dose COVID-19 vaccine programmes have already begun in Israel, and data about their effectiveness are starting to come in.Credit: Kobi Wolf/Bloomberg via Getty
To Eran Segal, a computational biologist at the Weizmann Institute of Science in Rehovot, Israel, who advises the Israeli government on COVID-19 issues, the implications are clear-cut. Theres compelling evidence that the third dose increases protection dramatically.
The bottom line, Morris says, is we need careful modelling and we need really thorough data to deconvolve all these things.
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How Effective Is Protection After A Single Dose Of Covid
Individuals who are partially vaccinated are insufficiently protected against the currently circulating variants of concern. While this was already the case with the Delta variant, the circulation of the Omicron variant highlights the importance of not only getting fully vaccinated as soon as possible but also of giving an additional or booster dose in the adult population.
This is critical to address issues of waning immunity following a full primary vaccination course, as well as to provide more protection against the new Omicron variant. Priority should be given to population groups at highest risk of severe outcomes following SARS-CoV-2 infection.
Two Doses Of J& j Vaccine Found To Provide Strong Protection Against Moderate
This study looked at the effects of a J& J booster shot given 56 days after a first dose. In the study, the two shots together provided about 94% protection against moderate-to-severe COVID-19 symptoms in the U.S. and 75% protection globally. They were also found to provide 100% protection against severe COVID-19 about 14 days after vaccination.
Data also shows that when a J& J booster shot is given 6 months after a first dose, antibody levels are about 12 times higher 4 weeks after the booster is given. Antibodies are substances our body makes in response to a foreign invader like COVID-19. Since the vaccines mimic infection, they prompt our immune systems to create antibodies that can recognize and attack the virus if we become infected.
But the single shot is still thought to be effective including against the Delta variant . Recent data shows that one dose of the J& J vaccine is 81% effective against COVID-19-related hospitalizations and 79% effective against infection.
These results havent been published in a peer-reviewed journal they were announced in a J& J press release.
To read more about this announcement, click or tap here.
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Modernas Vaccine May Work Better Against The Delta Variant Compared To Pfizers Vaccine
Overall, this study found that the Moderna vaccine was 86% effective against infection and the Pfizer vaccine was 76% effective. But during July, when Delta was announced as the main variant in the U.S., study data showed the Moderna vaccine was 76% effective against infection compared to Pfizers 42% in the study populations.
This study was conducted across five states, and it included about 74,000 fully vaccinated people. Of these, about 36,000 received the Moderna vaccine and almost 38,000 received the Pfizer vaccine.
What this means: In one health system, preliminary results from a recent study showed that the Moderna vaccine may be more effective than the Pfizer vaccine against the Delta variant. But the study ended by saying both vaccines are still considered highly protective against infection and severe disease.
What this doesnt mean: You should be concerned if you received a vaccine other than the Moderna vaccine.
To read more about this study, click or tap here.
It Takes A Couple Of Weeks
Clinical trials show COVID vaccine protection is optimal from about two weeks after your second dose. This means they:
nearly completely protect against severe disease and death in healthy people
dramatically reduce the likelihood of symptoms with COVID-19
reduce the likelihood of infection with the virus
if you do get infected, they reduce the amount of virus you make. Emerging evidence suggests this reduces the likelihood you will pass the virus to other people.
Each dose of a vaccine essentially shifts the odds in your favour. One dose gives you a lower chance of reaping some of these benefits, while two doses gives you a much higher likelihood of these benefits.
Though even with two doses, you could still be unlucky and get infected, develop disease or pass on the virus.
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Vaccines Appear Weak At Blocking Omicron Better Against Severe Disease
Vials with Pfizer-BioNTech and Moderna coronavirus disease vaccine labels are seen in this illustration picture taken March 19, 2021. REUTERS/Dado Ruvic/Illustration
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Vaccines appear weak vs Omicron infection, better vs severe disease
Vaccine effectiveness against symptomatic infection from the Omicron variant of the coronavirus is likely to be much lower than against earlier variants, but they may still offer substantial protection against severe disease, a new analysis suggests.
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Billy Gardner and Marm Kilpatrick from the University of California, Santa Cruz developed computer models incorporating data on COVID-19 vaccines’ efficacy against earlier variants and initial data on the Pfizer /BioNTech vaccine against Omicron. Their models suggest that early after two doses of an mRNA vaccine from Pfizer/BioNTech or Moderna , efficacy against symptomatic infection from Omicron is only about 30%, down from about 87% versus Delta, they reported on Sunday on medRxiv ahead of peer review. Protection against symptomatic infection is “essentially eliminated” for individuals vaccinated more than four months earlier. Boosters restore protection to about 48%, “which is similar to the protection of individuals with waned immunity against the Delta variant ,” Kilpatrick said.
COVID-19 vaccines may reduce long COVID burden
What If You Have A Weakened Immune System
The CDC already suggests a third dose of mRNA vaccine for people with weaker immune systems, especially those who are moderately to severely immunocompromised. This includes those who are getting cancer treatment, who have had a stem cell or organ transplant, who have advanced or untreated HIV, or who are taking certain medications.
Though not technically a booster shot, many people still call it that.
This extra dose, typically given a month or so after the second dose, is meant to increase the first immune response because:
- People with weaker immune systems are more likely to have serious, long-term illness from COVID-19.
- A weaker immune system may not respond as strongly to the vaccine and so may not make enough antibodies to fight off infection and serious illness from COVID-19.
- Even with a good vaccine response, people with weaker immune systems may benefit from extra protection against COVID-19.
If you have a weakened immune system and have had a third dose of the Pfizer or Moderna vaccine, talk to your doctor about whether you might need a booster shot.
U.S. Office of the Surgeon General.
Anthony Fauci, MD, director, National Institute of Allergy and Infectious Diseases.
CHEAC.org: FDA VRBPAC Votes to Recommend COVID-19 Boosters for Older Adults and High-Risk Groups.
Nature: Mix-and-match COVID vaccines ace the effectiveness test.
Mayo Clinic: COVID-19 vaccines for kids: What you need to know.
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Vaccine Protection Against Variants Of The Virus
It is normal for a virus to change. Different variants of the coronavirus SARS-CoV-2 have been found all over the world. Since there are only minimal differences between the variants and the original virus, the vaccine will not immediately become ineffective. Even if a vaccine is slightly less effective against a variant, it can still offer protection against serious illness and death.
When variants of the virus occur, they will be subjected to research at the national and international levels to determine how they respond to the vaccines.
RIVM is also conducting research on variants of the coronavirus SARS-CoV-2. Read more about that research: Variants of the coronavirus SARS-CoV-2.
How Long Are Covid
- Experts dont know yet how long COVID-19 vaccines will be effective.
- Studies of two of the most prominent COVID-19 vaccines suggest they remain effective for at least six months.
- The CEO of one vaccine maker said immunity may start to fade within a year.
One of the most pressing questions about COVID-19 vaccines is how long they can provide protection.
It may be decades, or a matter of months the data necessary to figure that out is accumulating every day. Pfizers CEO said this week that after a full regimen of doses immunity will probably start to fade within a year. According to the WHO, its simply too early to know the exact duration of COVID-19 vaccines because both the disease and the science deployed against it arent yet fully understood.
Some early evidence is promising. The viruses that caused MERS and SARS are closely related to the virus behind COVID-19, and acquired immunity to both of those diseases has proved relatively durable.
In terms of COVID-19-specific research, Pfizer and BioNTech said earlier this month that their vaccine remains effective for at least half a year after the second dose, and a study of Modernas version reflected a similar duration. Immunization efforts will have to play out further before we can know more for certain.
For more context, here are links to further reading from the World Economic Forum’s Strategic Intelligence platform:
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