The bottom line is that the original monovalent vaccines, whether as primary series or boosters, continue to provide strong and durable protection against severe disease.
Bivalent vaccines are here
The latest on who should take them
At a glance

After a very long time because of many regulatory and logistical issues, bivalent vaccines are finally available in the Philippines in limited quantities. Who should take them, and are they worth the wait?
The current bivalent vaccines are those Covid-19 vaccines that contain antigens against the original Wuhan strain as well as the BA.4/BA.5 Omicron sublineage in equal parts. The rationale for developing a bivalent vaccine is that the addition of the newer lineage might afford better protection against infection and severe disease since most circulating viruses at this point of the pandemic are Omicron and its sublineages. The data supporting this indication has been mixed, however, and not all scientists and physicians agree there is a significant advantage to the bivalent vaccines.
After reviewing the available data, the United States Centers for Disease Control (US CDC) concluded that bivalent vaccines add significant protection against hospitalization on top of the continued protection against severe disease from monovalent (old, Wuhan virus-based) vaccines. The US CDC therefore recommends that anyone above six months of age get at least one bivalent vaccine dose if their last monovalent dose was given more than two months ago. This is regardless of how many monovalent doses have been received. Subsequently, the US FDA approved bivalent vaccines for use as primary series vaccination as well, at which point the US stopped using monovalent vaccines altogether for any indication.
The World Health Organization (WHO), on the other hand, does not yet specifically recommend bivalent vaccines. WHO divides Covid-19-susceptible populations into high risk, medium risk, and low risk. High risk populations include the elderly, the immunocompromised, adults with comorbid conditions, and frontline health workers. For this population, WHO recommends second boosters without specifically mentioning bivalent vaccines.
Classified as medium risk and only needing one booster are otherwise healthy adults younger than 60 years old and children with comorbidities. Second boosters can be safely given for this population but the WHO does not require them since the evidence for any additional benefit is not strong. The low risk group, which includes healthy children and adolescents ages six months to 17 years, might need only the primary series. While boosters are safe in this population, there isn’t much evidence that there is significant incremental benefit from a public health standpoint.
These contrasting recommendations have led to a lot of confusion among people who are trying to figure out if they do need a second booster, let alone a bivalent vaccine. To add to the confusion, there is emerging evidence that bivalent vaccines may not work well in certain situations, especially if someone was previously infected by a non-Omicron virus. In these instances, the old virus strain may produce more antibodies than the Omicron component and not provide enough added protection against circulating Omicron viruses.
This finding has led the WHO to recommend that the development of subsequent future boosters be focused on only one virus strain rather than continuing to include the Wuhan strain in the formulation, and that this particular strain be an XBB sublineage rather than the current BA.4/BA.5 sublineage in the bivalent vaccines.
Having said all that, the preponderance of evidence suggests that a bivalent booster, whether as a first, second, or third booster, will still likely benefit the high-risk populations by adding significant protection against hospitalization. The priority groups for the limited bivalent vaccine supplies are therefore A1 (healthcare workers) and A2 (elderly persons 60 years old and older). Once a sufficient supply is available, other risk groups can be considered.
The end of the emergency phase of the pandemic is complicating the availability of bivalent vaccines, which are still under emergency use authorization (EUA). Since the validity of the EUA is tied to the state of calamity stemming from the pandemic emergency, there were some regulatory hurdles that had to be ironed out in order to receive the latest shipment of bivalent vaccines. Subsequent shipments are still uncertain.
A certificate of product registration (CPR) for bivalent vaccines will go a long way in solving this regulatory mess and I hope the FDA gives its approval soon. Many countries including the US with stringent FDAs have fully approved bivalent vaccines and so there seems to be good safety and scientific basis for local approval. In addition, a CPR will enable private physicians and hospitals to procure bivalent vaccines and administer these to patients as part of usual clinical practice. This will put less pressure on government as the sole source of vaccines.
In the meantime, the only way to receive the bivalent vaccines if you aren’t part of the priority population is to receive them abroad. This clearly isn’t an ideal situation but it is an option for those who have international travel plans. I received my bivalent vaccine in October 2022 when I was in the US for an infectious diseases conference and it was given for free.
When the US no longer renewed its state of emergency in May 2023 following the WHO declaration, the ability of foreign nationals to continue accessing the vaccines in this way was uncertain.
During our US vacation just this month, however, we were still able to access bivalent vaccines from the drugstore for my wife and my 15-year-old son. My 11-year-old daughter did not get a bivalent booster since we would have had to establish care with a pediatrician and the drug store did not have the pediatric formulation in stock. I think the US will continue to give free bivalent vaccines to everyone, including foreigners, for a few months after the end of the emergency since they still have vaccine stocks. It is rumored that the retail price of the Moderna bivalent vaccine will be about $140 and so if you are in the US any time soon it is best to take advantage of the free vaccine program while it is available.
The bottom line is that the original monovalent vaccines, whether as primary series or boosters, continue to provide strong and durable protection against severe disease. It is the original monovalent vaccines that enabled us to get out of the pandemic, and our protection will never go back down to zero. The bivalent vaccine’s role for now seems limited to the highest risk populations, although other risk groups can receive it. Updated monovalent vaccines are in the horizon, but their role for now also remains uncertain. Whatever happens, the original vaccines did the initial heavy lifting and updated vaccines will serve to improve upon their protection.