The coronavirus disease 2019 (COVID-19) pandemic, which was caused by the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to persist. The unrelenting nature of the COVID-19 pandemic is largely due to the rapid spread of many mutant SARS-CoV-2 variants that escape immunity elicited by prior infection and/or vaccination.
Among the several COVID-19 vaccines that are currently available, the COVID-19 Valneva vaccine (VLA2001) is an inactivated whole virus vaccine. This vaccine received marketing authorization in Europe in June 2022.
Recently, the World Health Organization (WHO) Strategic Advisory Group of Experts on Immunization (SAGE) published interim guidelines for its use.
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About the Valneva vaccine
The Valenva vaccine has been manufactured using purified SARS-CoV-2. This approach is already in use for many common vaccines, including seasonal influenza, polio, and pertussis vaccines. The inactivation of the virus prevents viral replication and infection.
The vaccine virus is adjuvanted with aluminum hydroxide (alum) in combination with CpG1018, a toll-like receptor 9 agonist, to improve its immunogenicity and shift the response towards a protective one. Moreover, the vaccine elicits immune responses against the SARS-CoV-2 spike protein, as well as other viral surface antigens.
The response
This vaccine induces neutralizing and other binding antibodies, as well as cellular type 1 T helper cell (Th1)-biased responses against SARS-CoV-2.
The Valneva vaccine is reported to be safe and effective in protecting against severe COVID-19 in people between the ages of 18 and 50 years. Its immunogenicity appears to be comparable to that of the earlier AstraZeneca viral vector vaccine ChAdOx1-S.
To date, there is a lack of research confirming whether the Valneva vaccine can prevent the transmission of SARS-CoV-2. Therefore, hand hygiene, respiratory hygiene, social distancing, proper ventilation indoors, and the use of a mask are recommended.
The extent to which the Valneva vaccine is effective against newer SARS-CoV-2 variants is still being investigated. Importantly, this vaccine is relatively less effective against the SARS-CoV-2 Delta and Omicron variants of concern (VOCs). In fact, neutralizing antibody titers against these strains were reduced by 2.7-fold and 16.7-fold, respectively, as compared to the ancestral variant.
Priority groups
The Valneva vaccine is proposed to be administered first to those at higher risk of infection, such as the elderly, health workers, and those with weakened immune systems. Potential immunocompromised patients who can benefit from this vaccine include those with current malignancy, immunodeficiency, or on immunosuppressants, as well as people infected with the human immunodeficiency virus (HIV), low CD4 cell levels, or with opportunistic infection with a positive viral load or not currently receiving treatment for HIV.
Immunocompromised people may not respond as well to the Valneva vaccine as others with a robust immune system. Thus, these individuals may require a third booster dose one to three months from completing their initial vaccination series. According to the WHO, close contacts of such individuals should also receive the vaccine in addition to taking other steps to avoid transmission of SARS-CoV-2 to these vulnerable individuals.
People in crowded living spaces, including refugees, prisons, and slums, should receive the vaccine earlier, as they cannot conform to public health measures to limit viral transmission. High-risk ethnic or demographic groups should also be identified and offered the vaccine early.
Individuals with prior infection
The Valneva vaccine may also be offered to those with a prior history of COVID-19, irrespective of whether their illness was symptomatic. To date, hybrid immunity is considered the most protective form of immunity against SARS-CoV-2.
Thus, some individuals may benefit from waiting three months after infection to get the vaccine to optimize the benefit of vaccination; however, further evidence is needed to standardize this practice.
Nevertheless, acute COVID-19 should not be followed immediately by vaccination, which should be delayed until convalescence is complete. Those who have received monoclonal antibodies or convalescent plasma to treat COVID-19 can receive the vaccination immediately; however, the antibody titers induced by the vaccine may be lower to some extent.
The effect of such a reduction on the ultimate degree of protection is unclear. However, the benefits appear to outweigh this potential risk.
Pregnancy and lactation
The Valneva vaccine is recommended for use in pregnancy by WHO since contracting COVID-19 is considered a greater danger to the mother during this time than possible adverse effects of the vaccine. Thus, it is not necessary to rule out pregnancy, delay conception, or abort a fetus because of vaccination, as it has not been proved to be teratogenic.
Breastfeeding women may also receive this vaccine, as evidenced by the benefit of this practice to both mother and baby, as well as its sustained effectiveness, irrespective of lactation. The WHO supports continuing breastfeeding after vaccination, as the virus within the vaccine cannot cause infection of the mother or infant.
Due to the current lack of data on the safety of the vaccine in people younger than 18 and older than 50, its use is currently limited to this category. Even among those eligible for the vaccine, anaphylaxis is an absolute contraindication to further doses. Anyone who has an acute reaction of fever should also delay vaccination as needed.
Vaccination course
The vaccine is given by intramuscular injection in two doses, separated by an interval of 28 days or more. A booster dose may be given to those with the highest risk, such as older adults, healthcare workers, and those with certain comorbid conditions. This dose is given four to six months from the second dose or if delayed beyond this point, at the earliest opportunity.
The Valneva vaccine is not recommended as a booster dose after completion of a primary course with a messenger ribonucleic acid (mRNA) vaccine; however, it may be used following two doses of ChAdOx1-S. Pending further study, this vaccine may not be used as a heterologous booster after primary vaccination with other COVID-19 vaccines, including other inactivated whole-virus vaccines.
Adverse reactions were mostly reported to be mild, with about 70% reporting local and systemic reactions. The most common reactions included local tenderness, headache, muscle pain, and tiredness, most of which resolved within two days for both the first and second doses.
Co-administration of other vaccines
The Valneva vaccine may be given along with other adult vaccines of various kinds; however, these vaccines should be administered at different sites and preferably on different limbs. Such patients should be followed up carefully. Combining such vaccines may reduce mortality and morbidity in older and sicker people, as well as others at higher risk for serious illness.
Continued surveillance
Post-authorization monitoring is required by the WHO, including vaccine effectiveness in all eligible groups, correlates of protection and durability, effectiveness against newer variants, and the effect on viral spread. The ability of the Valneva vaccine to prevent or mitigate post-COVID-19 conditions should also be investigated.
Special groups, including pregnant and breastfeeding women, should be analyzed separately. It is also important that researchers gather immunogenicity data in children and adolescents. Adverse event monitoring must also be maintained.
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