The CanSino Biologics Ad5-nCoV-S [recombinant] COVID-19 vaccine: What you need to know – World Health Organization

The WHO Strategic Advisory Group of Experts on Immunization (SAGE) has issued updated interim policy recommendations for the use of the Ad5-nCoV-S recombinant (Ad5-nCoV) vaccine against COVID-19. This article provides a summary of those interim recommendations; you may access the full guidance document here.
Here is what you need to know.
The vaccine is safe and effective for all individuals aged 18 and above. In line with the WHO Prioritization Roadmap  and the WHO Values Framework, older adults, health workers and immunocompromised persons should be prioritised.
The CanSino vaccine can be offered to people who have had COVID-19 in the past. But individuals may choose to delay vaccination for 3 months following the infection.
The available data on the Ad5-nCoV vaccine in pregnant women are insufficient to assess either vaccine efficacy or possible vaccine-associated risks in pregnancy. However, based on previous experience with other vaccines during pregnancy, the effectiveness of the Ad5-nCoVAd5-nCoV vaccine in pregnant women is expected to be comparable to that observed in non-pregnant women of similar age. Further studies are expected to evaluate safety and immunogenicity in pregnant women.
In the interim, WHO recommends the use of the Ad5-nCoV vaccine in pregnant women when the benefits of vaccination to the pregnant woman outweigh the potential risks. To help pregnant women make this assessment, they should be provided with information about the risks of COVID-19 in pregnancy; the likely benefits of vaccination in the local epidemiological context; and the current limitations of safety data in pregnant women. WHO does not recommend pregnancy testing prior to vaccination. WHO does not recommend delaying pregnancy or considering terminating pregnancy because of vaccination.
WHO recommends the same use of Ad5-nCoV vaccine in breastfeeding as in other adults. WHO does not recommend discontinuing breastfeeding following vaccination. 
A history of anaphylaxis to any component of the vaccine is considered a contraindication to vaccination.
Individuals with an immediate non-anaphylactic allergic reaction to the first dose (i.e. urticaria, angioedema without respiratory signs or symptoms that occur within 4 hours of administration) should not receive additional doses, unless recommended after review by a health professional with specialist expertise.  Similarly, anyone who experienced thrombotic thrombocytopenic syndrome (TTS) following the first dose of this vaccine should not receive a second dose of the same vaccine.
Persons with acute PCR-confirmed COVID-19 should not be vaccinated until after they have recovered from acute illness and the criteria for ending isolation have been met.
SAGE has thoroughly assessed the data on quality, safety and efficacy of this vaccine and has recommended its use for people aged 18 and above.
Thrombosis with thrombocytopenia syndrome (TTS), a very rare syndrome of blood clotting combined with low platelet counts, has been reported around 3–30 days following vaccination with Ad5-nCoV.  A causal relationship between the vaccine and Thrombosis with Thrombocytopenia Syndrome is considered plausible although more evidence is needed to confirm this.
In countries with ongoing SARS-CoV-2 transmission, the benefit of vaccination in protecting against COVID-19 far outweighs the risks of TTS. However, benefit–risk assessments may differ from country to country. As part of the EUL process, CanSino has committed to continuing submit data on safety, efficacy and quality in ongoing vaccine trials and rollout in populations, including in older adults.
Clinical trial data showed that the Ad5-nCoV vaccine had an efficacy of 58% against symptomatic disease and 92% against severe COVID-19.
SAGE recommends the use of Ad5-nCoV vaccine as a single dose (0.5 ml) given intramuscularly into the deltoid muscle.
In accordance with the WHO Prioritization Roadmap, a booster dose is recommended for the highest and high priority-use groups (i.e. older adults, health workers, persons with comorbidities), administered 4–6 months after completion of the primary series.
The Ad5-nCoV booster dose following a primary series with the inactivated COVID-19 vaccine developed by Sinovac (CoronaVac) was associated with higher vaccine effectiveness compared to a homologous CoronaVac booster. Ad5-nCoV vaccine may be used as a booster dose following a completed primary series using any other EUL COVID-19 vaccine.
Heterologous boosters should take into account current vaccine supply, vaccine supply projections, and other access considerations, alongside the potential benefits and risks of the specific products being used. 

As recent data suggest limited effect of the vaccine on transmission, particularly against Omicron, it is advisable that public health and social measures to reduce SARS-CoV‑2 transmission should be considered.  These measures include wearing a mask, physical distancing, handwashing, respiratory and cough hygiene, avoiding crowds and ensuring adequate ventilation according to local national advice.

The principal clinical trial for this product was completed in January 2021, before the emergence of Delta and Omicron variants. There are still insufficient data for these more recent variants.
SAGE currently recommends using this vaccine, according to the WHO Prioritization Roadmap.

We cannot easily compare vaccines head-to-head due to different approaches taken in designing the respective efficacy and effectiveness studies, but overall, all of the vaccines that have achieved WHO Emergency Use Listing can be considered safe and highly effective in preventing severe disease and hospitalization due to COVID-19.
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