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)hasissued 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 thefull guidancedocumenthere.

Here is what you need to know.

While COVID-19 vaccine supplies are limited, health workers at high risk of exposure and older people should be prioritised for vaccination.

Countries can refer to the WHO Prioritization Roadmap and the WHO Values Framework as guidance for their prioritisation of target groups.

The vaccine is not recommended for persons younger than 18 years of age, pending the results of further studied in that age group.

SAGE recommends the use of Ad5-nCoV vaccine as a single dose (0.5 ml) given intramuscularly into the deltoid muscle.

Vaccination is recommended for persons with comorbidities or certain health states that have been identified as increasing the risk of severe COVID-19, including diabetes mellitus, obesity, cardiovascular and respiratory disease and neurodegenerativedisease.

The vaccine can be offered to people who have had COVID-19 in the past. The optimal time interval between a natural infection and vaccination is not yet known. People who have had previous infection may choose to delay vaccination for 3 months followingthe infection. When more evidence becomes available, the length of this time period may be revised as well as the number of doses needed.

SAGE recommends that moderately and severely immunocompromised persons should be offered an additional (i.e. second) dose as part of the primary series 1-3 months after the first dose. This is due to the fact that this group are less likely to respondadequately to vaccination following standard primary vaccination series and are at higher risk of severe COVID-19, regardless of age.

For purposes of this interim recommendation, moderately and severely immunocompromised persons include those with active cancer, transplant recipients, immunodeficiency, and active treatment with immunosuppressives. It also includes people living withHIV with a current CD4 cell count of <200 cells/l, evidence of an opportunistic infection, not on HIV treatment, and/or with a detectable viral load (i.e. advanced HIV disease).

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 effectivenessof 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 informationabout 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 doesnot 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 afterreview 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.

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 abooster 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.

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 highlyeffective in preventing severe disease and hospitalization due to COVID-19.

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 330 days following vaccination with Ad5-nCoV. A causal relationship between the vaccine andTTS 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, benefitrisk assessments may differ from country to country. As part of the EUL process, CanSinohas 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.

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.

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-CoV2 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.

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