Some of theworld's leading vaccine makers are developing bird flu shots to prepare forpossible outbreaks of the sickness in humans.

Bird flu, or avian flu, is officially known as H5N1. The virususually spreads among different kinds ofpoultry.Human infections remain very rare. But most human cases have been linked todirect contact with infected birds.

Now, several large vaccine developers are working on bird fluvaccines to prepare for the possibility that the virus could one day jump tohumans.

One current outbreak involves an avian flu version that hasalready killed record numbers of birds and some other infected animals.

Officials at three major vaccine manufacturers told Reuters newsagency they are already developing and preparing to test vaccines to protectagainst new bird flu variants. The companies include Britain's GSK and CSLSeqirus and U.S.-based Moderna. Other vaccine makers told Reuters they"stand ready" to begin production efforts for bird flu if necessary.

In addition, there has been a push among companies to develop avaccine to be given directly to poultry. Such a market could be much largerthan the one for humans.

Vaccine company officials told Reuters that hundreds of millionsof bird flu shots could be manufactured within months if a new variant of thevirus starts spreading among humans.

Health experts have noted, however, that most new vaccinetreatments for avian flu would be set aside for wealthy nations that alreadyhave existing contracts with shot makers.

Many countries have pandemic plans in place that call for givingvaccines to the mostvulnerablepeoplefirst while supplies are limited. But during COVID-19, many vaccine-richcountries vaccinated large parts of their populations before consideringsharing shots.

Dr. Richard Hatchett is chief executive of the Coalition forEpidemic Preparedness Innovations (CEPI), an organization that helps financevaccine research. He told Reuters that possible human bird flu outbreaks couldlead to even greater "hoardingandvaccine nationalism" than during the COVID-19 pandemic.

An international agreement covering pandemic flu sets aside 10percent of worldwide supply for the World Health Organization to share withlow- and middle-income countries. But after the COVID-19 pandemic, the WHO hassought guarantees of 20 percent of the worldwide supply for use in otherpandemics.

The WHO says it has signed legally-backed agreements with 14manufacturers for 10 percent of their pandemic flu vaccine. The agreements callfor the vaccines to be provided as a mix of donated shots and those to bebought by the WHO. The agreements include six of the largest seasonal flumanufacturers, such as GSK, Sanofi and CSL Seqirus, the WHO said.

The WHO did not comment on possible vaccine hoarding during aflu pandemic. But it said policies were being developed "so that countriescan work together – not in competition with each other" to respond to sucha crisis. The WHO said it was "fullyconfident"that manufacturers and member states would follow the policies.