A Phase 3 interventional study of Vaccine and Placebo in RSV Infections, RSV Immunisation and Preterm Labour, sponsored by University of Witwatersrand, South Africa. Recruiting at 11 sites in 4 countries. Open to female participants aged 14 Years to 55 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-05-18.
Sponsored by University of Witwatersrand, South Africa · Phase 3, Interventional, and Prevention
Respiratory syncytial virus (RSV) is a virus that often affects children during childhood. Even though most cases of RSV are mild, it can cause serious disease and even death - especially in very young babies, babies born too early and those born with heart and lung problems. It is the most common cause for children under 5 years old to be hospitalised. In 2019, there were about 33 million RSV-infections in the lower respiratory tract (in the lungs and below the voice box) of which 3,6 million people were hospitalised and 26,300 passed away in hospital due to RSV. Almost half (50%) of deaths that are caused by RSV, happen in children younger than 6 months old and the majority (more than 95%) of these deaths happen to infants and children in low- and middle-income countries.
A way that can help protect babies from becoming infected is through giving vaccines against the germ (RSV) that is targeted for prevention. There are currently no registered vaccines that can be given directly to babies however there is a lot of information available that shows that a vaccine can be safely giving to a mother while she is still pregnant. The mother then produces antibodies (protection cells) that is transferred to the baby before the baby is born, and the baby is protected from getting sick during the first few months of life.
One of the vaccines that has been developed (ABRYSVO) has been used in many clinical trials in pregnant moms (and older people) to test if it is safe and will protect young babies and much older people who are all at the highest risk for a severe RSV disease. The vaccine was given to more than 4,000 pregnant women. The results from the study and previous studies showed that the vaccine was safe and the babies had a lower chance of getting severe RSV disease and going to hospital. It showed that the vaccine prevented severe RSV infection in around 80% of babies younger than 90 days, and 70% of babies younger than 6 months. Therefore, the vaccine has been licensed in a few countries around the world (including the United States of America and other high-income countries) which means that pregnant women can receive this vaccine during their pregnancy if they wish to (without being on a clinical trial). It has also been licensed in South Africa but is not yet available in the country for pregnant women to receive. The licensure is also underway in other African countries.
However, the results of the previous studies of this vaccine also showed that a slightly higher number of premature babies were born to women who received the vaccine compared to women who did not receive the vaccine. The information received from these studies was however not enough to decide if the earlier births were related to the vaccine or not, and more information is needed - which is one of the main reasons for this study. Importantly, all of the babies who were born earlier were only born a few weeks earlier than expected (around 35 weeks of pregnancy), and all the babies were well and survived. The previous studies on this vaccine happened during the COVID-19 pandemic at which time people were wearing masks and contacting other people less therefore not spreading RSV around as we would normally expect. By doing this study, it will assist the investigators to determine if the vaccine is really as good as it is perceived to be for preventing serious RSV illness in the babies.
This RSV vaccine is a very important medical intervention, and it is as important that the effect that this vaccine will have on pregnant women and on the infants born to mothers who receive the vaccine can be measured. It is especially important in African and lower-middle income countries as the vaccine was not tested as much in people living in Africa compared to others. Therefore, the main reason for doing this trial is to see how much value the vaccine can bring to these countries in terms of protecting young babies and infants where many may get a severe infection and be hospitalised. It will also measure if the vaccine does increase the chances of a baby being born earlier than expected. It will only be carried out in the countries after the vaccine has been approved for use by pregnant women (at the right time) as part of their pregnancy care.
306 studies on the registry are indexed under Respiratory Syncytial Virus Infections; 50 are open to participants now.
This study's planned enrollment of 13,000 is above the median of 89 across 223 interventional studies indexed under Respiratory Syncytial Virus Infections.
Browse Respiratory Syncytial Virus Infections studies →University of Witwatersrand, South Africa is the lead sponsor of 47 studies on the registry; 4 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Current pregnancy complications or abnormalities at the time of consent that will increase the risk associated with the participation in and completion of the trial, including but not limited to the following:
At least THREE prior pregnancy complications or abnormalities at the time of consent, based on the investigator's judgment, that will increase the risk associated with the participation in and completion of the trial, including but not limited to the following:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Control group will receive the placebo which will match the vaccine to maintain the blind but will not contain any active product. Participants will be randomised 1:1
Other: Placebo
ABRYSVO vaccine developed by Pfizer. The active ingredients in RSVpre-F are 2 stabilized RSV prefusion F antigens, in equal amounts from virus subgroups A and B, in a lyophilized dosage form for reconstitution
Drug: Vaccine
The active ingredients in RSVpreF are 2 stabilized RSV prefusion F antigens, in equal amounts from virus subgroups A and B, in a lyophilized dosage form for reconstitution.
Placebo matched to vaccine but not containing any active ingredients
Evaluate the efficacy of RSVA/B-preF against RSV-A or RSV-B subtype confirmed severe LRTI through to 180 days of age by measuring the first occurrence of RT-PCR confirmed RSV severe LRTI
The presence of LRTI will be confirmed according to case definition. The severity of LRTI will be based on the WHO grading criteria
Time frame: From infant birth to 180 days of age
Evaluate the safety of RSVA/B-preF in relation to preterm births in women with gestational age (GA) staging Level of Certainty [LOC] 1 to 2B at time of enrolment by measuring the occurrence of preterm births (<37 weeks GA)
The GA staging will be based on Global Alignment on Immunization safety Assessment (GAIA) criteria
Time frame: At delivery of the infant
Evaluate the efficacy of RSVA/B-preF against RSV-confirmed severe LRTI through to 90, 120 and 150 days of age by measuring the first occurrence of RT-PCR confirmed RSVA or RSVB severe LRTI
Time frame: 90, 120 and 150 days of age
Evaluate the efficacy of RSVA/B-preF against RSV-confirmed LRTI resulting in hospitalization with use of supplemental oxygen OR O2 saturation of <92% (at 180 days, 90, 120 & 150 days) by measuring the first occurrence of RT-PCR confirmed RSVA or RSVB
Time frame: At 90, 120, 150 and 180 days of age
Evaluate the efficacy of RSVA/B-preF against RSV-confirmed MA-LRTI and very-severe LRTI (at 180 days, and 90, 120 and 150 days) by measuring the first occurrence of RT-PCR confirmed RSVA or RSVB MALRTI or very-severe LRTI
Time frame: 90, 120, 150 and 180 days of age
Evaluate the efficacy of RSVA/B-preF against RSV-confirmed: a. MA-LRTI; b. severe-LRTI; c. very-severe LRTI; d. LRTI hospitalization from 0 to 90 days and 91-180 days by measuring the first occurrence of RT-PCR confirmed RSVA or RSVB MA-LRTI
Time frame: 0-90 and 91-180 days of age
Evaluate the efficacy of RSVA/B-preF against all-cause: a. MA-LRTI; b. severe LRTI; c. very-severe LRTI; d. LRTI hospitalization, by measuring the first occurrence of all-cause MALRTI
Time frame: at 180 days, and 90, 120, and 150 days; and at 0-90 days and 91-180 days of age
Evaluate the safety of RSVA/B-preF against prematurity in women vaccinated at 28 to <32 weeks, 32 to 36 weeks by measuring the occurrence of pre-term delivery (<37 weeks)
Limited to women with GA staging using GAIA LOC 1 to 2B at time of enrolment
Time frame: At delivery of the infant
Evaluate the safety of RSVA/B-preF against prematurity occurring at 28 to <32 weeks, 32 to 36 weeks by measuring the occurrence of pre-term delivery in the mentioned intervals
Limited to women with GA staging using GAIA LOC 1 to 2B at time of enrolment
Time frame: At delivery of the infant
Evaluate the safety of RSVA/B-preF against low birth weight (<2500 grams) and very low birth weight (<1500 grams) by measuring the occurrence of low and very low birth weights
Time frame: At delivery of the infant
Plan to share: Yes — Progress reports for this trial will be made available to the trial funder, ethics committees, regulatory authorities and other stakeholders. Final trial results will be shared with the same stakeholders within 3 months of final lock of the trial database. Study data will be shared with Pfizer in the event of safety concerns or a request from a regulatory agency. Manuscript(s) will be prepared and submitted for peer-review in open access journals. All proposed publications will first be reviewed by Pfizer prior to publication for review of potential confidential information. A publication plan and proposal for criteria of authorship will be established with the sites. The trial database will be made publicly available upon request. Any transfer of data, will be governed, by the terms of the local Ethics Committee (HREC).
Supporting information: Clinical study report, Analytic code
Time frame: Within 12 months of availability of study report
Access criteria: Any transfer of data, will be governed, by the terms of the local Ethics Committee (HREC). Data sharing will be done on a collaborative basis, with the site PI (or his nominee) being included in any further interrogation of the data.
No publications or documents are linked to this record.
Started Sep 2025 (actual). Primary completion is estimated for Feb 2028, 29 months after the start.
Of 32 phase 3 interventional studies under Respiratory Syncytial Virus Infections, half reached primary completion within 8 months of starting (the median), counting those still running; a quarter within 6 and three quarters within 23. This study's planned 29 months is above that.
How these figures are worked out, and which studies are left out of them.
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Respiratory Syncytial Virus Infections →
University of Witwatersrand, South Africa